Force Determination Employing Sheet Sensor and Capacitive Array

ABSTRACT

A device configured to sense a touch on a surface of the device. The device includes a cover and a force-sensing structure disposed below the cover. The force-sensing structure may be positioned below a display and used in combination with other force-sensing elements to estimate the force of a touch on the cover of a device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/727,601, filed Jun. 1, 2015, and titled “Force DeterminationEmploying Sheet Sensor and Capacitive Array,” which is a continuation ofU.S. patent application Ser. No. 14/619,807, filed Feb. 11, 2015, andtitled “Force Determination Employing Sheet Sensor and CapacitiveArray,” now abandoned, which claims priority to U.S. Provisional PatentApplication No. 62/047,645, filed Sep. 8, 2014, and titled “ForceDetermination Employing Sheet Sensors and Capacitive Array,” U.S.Provisional Patent Application No. 61/941,988, filed Feb. 19, 2014, andtitled “Force Determination Employing Sheet Sensors and CapacitiveArray,” and U.S. Provisional Patent Application No. 61/939,252, filedFeb. 12, 2014, and titled “Force Determination Employing MultipleForce-Sensing Structures,” the disclosure of each of which isincorporated by reference in its entirety.

TECHNICAL FIELD

This application generally relates to systems and methods sensing theforce of a touch, and in particular to a capacitive force sensorintegrated with a device for detecting and measuring the amount ormagnitude of a touch applied to a surface of the device.

BACKGROUND

Touch devices can be generally characterized as devices that are capableof receiving touch input on the surface of the device. The input mayinclude the location of one or more touches on the device, which may beinterpreted as a command, gesture, or other type of user input. In oneexample, touch input on a touch device may be relayed to an a computingsystem and used to interpret user interaction with a graphical userinterface (GUI), including, for example, selecting elements on adisplay, reorienting or repositioning elements on a display, enteringtext, and user input. In another example, touch input on a touch devicemay be relayed to a computer system and used to interpret a user'sinteraction with an application program. The user's interaction mayinclude, for example, the manipulation of audio, video, photographs,presentations, text, and the like.

Typically, touch input on a touch device is limited to the location of atouch on the device. However, in some cases, it may be advantageous toalso detect and measure the force of a touch that is applied to thedevice. For example, it might be advantageous for a user to be able tomanipulate a computer-generated object on a display in a first way usinga relatively light touch and, alternatively, interact with the object asecond way using a relatively heavy or sharper touch. By way of example,it might be advantageous for a user to move a computer-generated objecton the display using a relatively light touch and then, alternatively,select or invoke a command with respect to the same computer using arelatively heavy or sharper touch. More generally, it might beadvantageous for the user to be able to provide input in multiple waysdepending on the force of the touch. For example, a user may provideinput that is interpreted a first way for a light touch, a second wayfor a medium touch, and a third way for a heavy touch, and so on.Additionally, it might be advantageous for the user to be able toprovide an analog input using a varying amount of force. This type ofinput may be useful for controlling, for example, a gas pedal on asimulated car or a control surface of an airplane in a flight simulator,or similar applications. It may be further advantageous for the user tobe able to provide input, such as simulated body movements or otherwise,in a virtual reality (VR) simulation (possibly with haptic feedback), orin an augmented reality program. It might be further advantageous to usethe force of a touch to interpret the relative degree (e.g., force) andlocations of multiple touches that are provided to multiple userinterface objects or elements that are in use on a touch device at thesame time. For example, the force of a touch could be used to interpretmultiple touches due to a user pressing more than one element in anapplication for playing a musical instrument. In particular, the forceof multiple touches may be used for interpreting multiple touches by auser on the keys of a piano. Similarly, the force of multiple touchescan be used to interpret a user's multiple touches in an application forcontrolling a motor vehicle (having separate controls for accelerating,braking, signaling, and turning).

SUMMARY

This application provides techniques, which can be used to measure ordetermine the amount or magnitude of force applied, and changes in theamount or magnitude of force applied, by a user contacting a touchdevice (such as a touch-sensitive surface, one example of which is atouch display), or other pressure-sensitive input elements (such as avirtual analog control or keyboard), or other input device. Thesetechniques can be incorporated into various devices using touchrecognition, touch elements of a GUI, and touch input or manipulation inan application program, such as touch devices, touch pads, and touchscreens. This application also provides systems and techniques that canbe used to measure or determine the amount or magnitude of forceapplied, and changes in the amount or magnitude of force applied, by theuser when contacting a touch device, and in response thereto, provideadditional functions available to a user of a touch device.

Certain embodiments described herein are directed to a force sensor,also referred to as a “force-sensing structure” or a “force sensitivesensor.” The force sensor may be integrated with the housing of anelectronic device, one example of which is a touch sensitive electricaldevice or simply a touch device. A sample force sensor may include anupper portion and a lower portion separated by a compressible element orby an air gap. The upper portion may include an upper body connected toan upper capacitive plate and the lower portion may include a lower bodyconnected to a lower capacitive plate. In some cases, the upper portionand the lower portion form a capacitor that can be used to measure ordetect an amount or magnitude of applied force. The compressible elementis typically formed form a compliant or springy material. In some cases,the compressible element is referred to as a “deformable middle body,”an intermediate element, or a “compressible layer.” In some cases, theforce sensor includes other force-sensing elements, such as a resistivestrain gauge, piezoelectric element, and the like.

Some example embodiments are directed to an electronic device having acover, a display positioned below the cover, and a force-sensingstructure disposed below the display. The force-sensing structure mayinclude an upper capacitive plate, a compressible element disposed onone side of the upper capacitive plate, and a lower capacitive platedisposed on a side of the compressible element that is opposite theupper capacitive plate. The force-sensing structure may also include aplate affixed to and supporting the force-sensing structure. In someembodiments, the electronic device also includes sensing circuitry thatis operatively coupled to the force-sensing structure. The sensingcircuitry may be configured to estimate the force of a touch on thecover based on a change in capacitance between the upper capacitiveplate and the lower capacitive plate of the force-sensing structure.

In some embodiments, the force-sensing structure is separated from thedisplay by a compliant layer including an air gap. In some cases, theforce-sensing structure is separated from the display by a compliantlayer comprised of compressible foam. The force-sensing structure may beseparated from the display by a compliant layer comprised of an array ofcompliant pillars and an optically transparent fluid.

In some embodiments, the electronic device also includes a housinghaving a bezel surrounding the cover and a gasket disposed in a gapbetween the cover and the bezel. The device may also include anoleophobic coating disposed over at least a portion of the gap.

Some example embodiments are directed to an electronic device includinga housing, a cover disposed within an opening of the housing, and astrain-sensitive gasket disposed between the cover and the housing alonga perimeter of the cover. The device may also include a force-sensingstructure disposed below the cover. The device may also include a platefixed relative to the housing and supporting the force-sensingstructure. In some cases, the strain-sensitive gasket includes a gasketupper capacitive plate, a gasket lower capacitive plate, and a gasketcompressible element disposed between the gasket upper capacitive plateand the gasket lower capacitive plate.

In some embodiments, the electronic device also includes a displaydisposed between the cover and the force-sensing structure, and acompressible layer comprising an air gap between the display and theforce-sensing structure. In some implementations, the air gap of thecompressible layer is configured to at least partially collapse inresponse to a force of a touch that exceeds a first threshold. The firstthreshold may be less than a second threshold that corresponds to amaximum force that can be detected by the strain-sensitive gasket.

In some embodiments, the electronic device also includes a displaydisposed between the cover and the force-sensing structure, and acompressible layer between the display and the force-sensing structure.In some cases, the compressible layer may be configured to at leastpartially collapse in response to a force of a touch that exceeds afirst threshold. The first threshold may be less than a second thresholdthat corresponds to a maximum force that can be detected by thestrain-sensitive gasket.

In some embodiments, the force-sensing structure includes: an uppercapacitive plate, a lower capacitive plate; and a compressible elementdisposed between the upper capacitive plate and the lower capacitiveplate. In some embodiments, the force-sensing structure includes astrain gauge and/or a piezoelectric element.

Some example embodiments are directed to an electronic device includinga cover, a capacitive sense layer positioned below the cover, and acompressible layer below the capacitive sense layer. In someembodiments, the compressible layer comprises an air gap. The electronicdevice may also include a force-sensing structure disposed below thecompressible layer, which includes an upper capacitive plate, acompressible element disposed on one side of the upper capacitive plate,and a lower capacitive plate disposed on a side of the compressibleelement that is opposite the upper capacitive plate. Some embodimentsinclude a plate positioned below the force-sensing structure andsupporting the force-sensing structure.

In some embodiments, the electronic device includes a display positionedbelow the cover. The device may also include a backlight positionedbelow the display. The capacitive sense layer may be disposed betweenthe display and the backlight.

In some embodiments, the electronic device includes sensing circuitrythat is operatively coupled to the capacitive sense layer and theforce-sensing structure. The sensing circuitry may be configured toestimate the force of a touch on the cover based on a change in mutualcapacitance between the capacitive sense layer and the upper capacitiveplate of the force-sensing structure. In some embodiments, the sensingcircuitry may be configured to obtain a first capacitance between theupper capacitive plate and the lower capacitive plate of the forcesensing structure. The circuitry may also be configured to obtain asecond capacitance between the upper capacitive plate and the capacitivesense layer. The circuitry may also be configured to generate anestimate of a force of a touch on the cover using the first and secondcapacitances.

While multiple embodiments are disclosed, including variations thereof,still other embodiments of the present disclosure will become apparentto those skilled in the art from the following detailed description,which shows and describes illustrative embodiments of the disclosure. Aswill be realized, the disclosure is capable of modifications in variousobvious aspects, all without departing from the spirit and scope of thepresent disclosure. Accordingly, the drawings and detailed descriptionare to be regarded as illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example touch device.

FIG. 2A depicts a cross-sectional view taken along line 1-1 of FIG. 1,of an example touch device having a force-sensing structure.

FIG. 2B depicts a cross-sectional view taken along line 1-1 of FIG. 1,of an example touch device having an alternative force-sensingstructure.

FIG. 3 depicts a cross-sectional view taken along line 2-2 of FIG. 2, ofan example touch device having a force-sensing structure.

FIG. 4 depicts a cross-sectional view taken along line 2-2 of FIG. 2, ofan example touch device having a force-sensing structure.

FIG. 5 depicts a cross-sectional view taken along line 2-2 of FIG. 2, ofan example touch device having a force-sensing structure.

FIG. 6 depicts a cross-sectional view of an embodiment of a touch devicehaving a capacitive force sensor.

FIG. 7 depicts another embodiment of a touch device having a capacitiveforce sensor.

FIG. 8 depicts a cross sectional view of another embodiment of a touchdevice having a capacitive force sensor.

FIG. 9 depicts an exemplary communication between a touch I/O device anda computing system.

FIG. 10 depicts a schematic of a system including a force sensitivetouch device.

FIG. 11A depicts an example method of operation.

FIG. 11B depicts another example method of operation.

FIG. 12 depicts a force-sensitive structure having an electricalconnector tail.

FIG. 13 depicts a cross-sectional view of an electrical connector tail.

FIG. 14 depicts an example method of manufacturing a force-sensitivestructure having an electrical connector tail.

FIG. 15A depicts a sample cross-section of another force-sensitivestructure incorporated into an electronic device.

FIG. 15B depicts a sample cross-section of still another force-sensitivestructure incorporated into an electronic device.

FIG. 15C depicts a sample cross-section of yet another force-sensitivestructure incorporated into an electronic device.

FIGS. 15D-E depict a portion of the cross-section of FIG. 15C in greaterdetail.

FIG. 16 depicts a sample cross-section of an electronic deviceincorporating two force-sensitive structures.

FIG. 17 depicts a sample cross-section of an electronic deviceincorporating a multi-layered sheet force sensor, coupled with acapacitive sensing array positioned in a display stack.

DETAILED DESCRIPTION

Generally, embodiments may take the form of an electronic device capableof sensing force and distinguishing between multiple different levels offorce, beyond simple binary sensing. Some embodiments may have anenclosure incorporating a force sensor therein (e.g., a force-sensitivesensor, a force-sensing element, or force-sensing structure). The forcesensor may be incorporated in, for example in a groove, cutout, oraperture formed in one or more sidewalls or other surfaces of thedevice. The force-sensing element may extend along an entire periphery,sidewall, or set of sidewalls in certain embodiments. For example, theforce sensor may encircle an interior cavity formed within the device,or may otherwise extend around an interior of the device. As force isexerted on an exterior of the device, such as an upper surface, theforce sensor may detect the force and generate a corresponding inputsignal to the device.

Some embodiments may incorporate multiple force sensors spaced about aperimeter of the electronic device, rather than a single force-sensingstructure or element. Further, the multiple force sensors need not forma continuous array or structure, but may be discretely spaced from oneanother. The number of force sensors may vary between embodiments, asmay the spacing. Each force sensor may sense a force exerted on anadjacent or nearby surface within a certain region of the device. Thus,a force exerted at a point that is between two underlying force sensorsmay be sensed by both.

Generally, the force sensor or device may include one or more capacitiveplates, traces, flex, or the like that are separated by a compressibleelement (e.g., a compliant member). As a force is transmitted throughthe device enclosure and to the force sensor, the compressible elementmay compress, thereby bringing the capacitive plates closer together.The change in distance between the capacitive plates may increase ameasured capacitance therebetween. A circuit may measure this change incapacitance and output a signal that varies with the change incapacitance. A processor, integrated circuit or other electronic elementmay correlate the change in capacitance to a force exerted on theenclosure, thereby facilitating the detection, measurement, and use offorce as an input to an electronic device. Although the term “plate” maybe used to describe the capacitive elements, it should be appreciatedthat the capacitive elements need not be rigid but may instead beflexible (as in the case of a trace or flex).

-   -   1. Terminology

The following terminology is exemplary, and not intended to be limitingin any way.

The text “applied force”, and variants thereof, generally refers to theforce of a touch applied to a surface of the device. Generally, thedegree, amount, or magnitude of the applied force can be detected andmeasured using the techniques described herein. The degree, amount, ormagnitude of an applied force need not have any particular scale. Forexample, the measure of applied force can be linear, logarithmic, orotherwise nonlinear, and can be adjusted periodically (or otherwise,such as aperiodically, or otherwise from time to time) in response toone or more factors, either relating to applied force, location oftouch, time, or otherwise.

The text “finger”, and variants thereof, generally refers to a user'sfinger, or other body part. For example and without limitation, a“finger” can include any part of the user's finger or thumb and any partof the user's hand. A “finger” may also include any covering on theuser's finger, thumb, or hand.

The text “touch,” and variants thereof, generally refers to the act ofan object coming into contact with a surface of a device. The object mayinclude a user's finger, a stylus or other pointing object. Exampleobjects include, a hard stylus, a soft stylus, a pen, finger, thumb orother part of the user's hand. A “touch” typically has an applied forceand a location that can detected and measured using the techniquesdescribed herein.

After reading this document, those skilled in the art would recognizethat these statements of terminology would be applicable to techniques,methods, physical elements, and systems (whether currently known orotherwise), including extensions thereof inferred or inferable by thoseskilled in the art after reading this application Likewise, it should beappreciated that any dimensions set forth herein are meant to beexamples only, and may change from embodiment to embodiment.

-   -   2. Force-Sensitive Device

In one embodiment, a force sensitive device and system can include acover glass element, such as a relatively transparent (in most or alllocations) substance capable of isolating circuitry or other internalelements of the touch device from external objects. The term “glass”refers to the relatively hard sheet-like qualities of the material anddoes not limit the material of the cover glass element to only glassmaterials. The cover glass element may be made from a variety ofmaterials including, for example, glass, treated glass, plastic, treatedplastic, and sapphire. In many cases, the cover glass is transparent,however it is not necessary that the cover glass be completely or evenpartially transparent. The cover glass can be disposed in asubstantially rectilinear shape, such as to cover the circuit for thetouch device and to serve as a touch plate for the user. The cover glassmay also be formed in a variety of other shapes depending on theapplication.

In some embodiments, the cover glass is integrated with or attached to atransparent or non-transparent touch sensor that is configured to detectthe location of a touch. The transparent touch sensor may be acapacitive touch sensor formed from one or more arrays of transparentconductive lines. For example, the transparent touch sensor may be amutually capacitive touch sensor formed from two arrays of transversetransparent conductive lines operatively coupled to touch sensingcircuitry. Such a transparent touch sensor may be able to detect andtrack multiple touches on the surface of the cover glass. The touchesmay include multiple finger touches, multiple stylus touches, or acombination of different types of touches on the cover glass. Othertypes of transparent touch sensors may also be used, including, forexample, self-capacitive touch sensors, resistive touch sensors, and thelike.

In one embodiment, the cover glass element is coupled to a frame orhousing for the touch device, such as a case constructed of metal,elastomer, plastic, a combination thereof, or some other substance. Insuch cases, the frame for the touch device can include a shelf or ledgeon which the cover glass element is positioned. The cover glass istypically positioned above the circuitry for the touch device. Forexample, the frame can include a shelf on which an edge of the coverglass element is positioned, with the (or some of the) remainder of thecover glass element positioned over the circuitry for the touch device.

In many of the embodiments described herein, a force sensor, (e.g. aforce-sensing structure, force-sensing element, or force sensitivesensor), is positioned below the cover glass and the shelf or ledge ofthe frame or housing. The force sensor typically includes a compressibleelement and is configured to detect and measure a relative displacementbetween the cover glass and the frame or housing. As previouslymentioned, the amount that the cover glass is displaced can be used toestimate the applied force. The following embodiments are directed todifferent techniques and methods of detecting and measuring thisdisplacement.

-   -   3. Exemplary Devices having a Force Sensor

FIG. 1 depicts an exemplary device 100 that incorporates one or moreforce-sensing structures, as described herein. With respect to FIG. 1,the device 100 is depicted as a tablet computing device, but it shouldbe appreciated that it may also be any of a number of other devices,including a mobile phone, portable computer, wearable device, touchscreen, and the like. The device 100 may have an enclosure 102 includingmultiple sidewalls and a bezel 106. In other embodiments, the device 100may be flush-mounted into a larger surface or enclosure and so thedevice may lack an identifiable bezel or sidewall.

As shown in FIG. 1, the electronic device 100 includes an electronicdisplay, located beneath a cover glass 104, for conveying graphicaland/or textual information to the user. The electronic display mayinclude a liquid crystal display (LCD), organic light omitting diode(OLED), or other electronic display component. In some embodiments, thedisplay may be omitted. For example, the cover glass may be placed overa control button or track pad that is not configured to convey graphicaland/or textual information to the user. (In such a case, the cover glassmay not be transparent.)

As shown in FIG. 1, the device includes multiple ports and mechanismsfor electrically and mechanically coupling the device to externaldevices or elements. The input mechanisms, ports, and the like may varybetween versions, types and styles of the electronic device 100.Accordingly, they are shown in FIG. 1 only as examples of such devicesand in sample positions.

FIG. 2A depicts a cross-sectional view taken along line 1-1, shown inFIG. 1. The cross-sectional view depicts the interior of a device 100having one type of force-sensing structure. A central portion of theenclosure 102 may enclosure electronic circuitry, mechanical structures,and other internal elements. As shown in the figure, a bezel 106 isformed around the perimeter of the device 100.

A ledge 202 may be formed along the perimeter of the bezel 106. Theexact dimensions of the ledge 202 may vary between embodiments. In thisembodiment, the ledge 202 includes a width configured to support thebase of a force-sensing structure 200. The base of the force-sensingstructure 200 may abut and attach to the top of the ledge 202 in certainembodiments. Likewise, as shown in FIG. 2A, an inner edge of theforce-sensing structure 200 may be parallel and approximately alignedwith an inner surface of the bezel 106. In other embodiments, the inneredge of the force-sensing structure 200 may be offset from an inner edgeof the bezel 106.

As shown in FIG. 2A, a single force-sensing structure 200 may encirclethe entirety of the inner cavity of the enclosure 102. That is, theforce-sensing structure 200 may extend along the entirety of theperimeter of the device and along the ledge 202. Thus, it may beappreciated that the force-sensing structure 200 may be formed as asingle unit or element.

FIG. 2B depicts an alternate cross-sectional view taken along line 1-1,shown in FIG. 1. As shown in FIG. 2B, the device 100 b includes analternative force-sensing structure 200 b. In the alternative embodimentof FIG. 2B, multiple force-sensing structures 200 b may be placed atdifferent locations along the perimeter of the bezel 106. In thisexample, a force-sensing structure 200 b is placed at or near each edgeof the bezel 106 of the electronic device 100 b. Additionally, aforce-sensing structure 200 c is placed at each of the corners of thebezel. Thus, in the example device 100 b shown in FIG. 2B, there areeight force-sensing structures (200 b, 200 c).

With regard to FIG. 2B, it should be appreciated that more or fewerforce-sensing structures 200 b may be used. For example, threeforce-sensing structures 200 b may be used and a location of a force maybe triangulated by comparing the outputs of each device. Alternately, anarray of more than four force-sensing structures 200 b may be used in adevice. Additionally, each of the force-sensing structures shown in FIG.2B may represent a number of individual force-sensing structures in alinear or two-dimensional array, for example. Accordingly, the numberand positioning of the various force-sensing structures 200 b depictedin FIG. 2B is merely exemplary and other variations are possible.

FIG. 3 depicts a cross-sectional view taken along 2-2 of the electronicdevice 100, as shown in FIG. 2A. As shown in FIG. 3, the physicalrelationship between the cover glass 104, bezel 106, and force-sensingstructure 300 is shown in more detail, although it should be appreciatedthat the exact geometry, sizes, tolerances, positions and the like mayvary. As shown in FIG. 3, the force-sensing structure 300 may be mountedor otherwise be positioned beneath a portion of the cover glass 104. Adisplay element 304 may likewise be positioned beneath the cover glass104. In some embodiments, the force-sensing structure 300 may beconcealed from external view by an ink or print layer deposited on thecover glass between the cover glass 104 and the force-sensing structure300. In other embodiments, the ink or print layer may be omitted.

In some embodiments, the display element 304 may act as an shield toelectrically isolate the force-sensing structure from other componentswithin the electronic device. Likewise, a shield may be formed on theledge 202 and portion of the housing 102 adjacent the gap 302 in orderto electrically isolate the force-sensing structure 300 from externalsignals, or at least reduce the impact of external noise on theforce-sensing structure. The shield layers may be deposited by physicalvapor deposition, as one non-limiting example. Further, any or all ofthe shield layers may extend into the interior of the electronic deviceto connect to a common or system ground. For example, the shield layermay extend from the ledge down the interior wall of the enclosure 102 toa system ground.

In certain embodiments, the ledge and/or portion of the housing maythemselves act as shielding structures, rather than having any shieldformed thereon. It should be appreciated that one or more of the variousshield layers/structures may be electrically tied to one another incertain embodiments, although this is not necessary.

As shown in FIG. 3, the bezel 106 is adjacent to the ledge 202, which isrecessed from the surface of the bezel 106 and is configured to supportthe force-sensing structure 300. As shown in FIG. 3, a gap 302 may existbetween the interior edge of the bezel 106 and the outer edge of thecover glass 104. The gap may allow free movement of the cover glass 104with respect to the enclosure 102.

In certain embodiments, a portion or all of the surfaces of the gap 302may be coated with an oleophobic material. The oleophobic material mayserve as a barrier against, or repel, oils, dust, dirt and other similarmaterials from entering the gap 302 and/or impacting the force-sensingstructure 300. In this fashion the coating may serve to maintainoperation of the force-sensing structure over time. Coatings other thanan oleophobic coating may be used; other dust-and/or oil- and/ordirt-repellent coatings may be used in different embodiments.

As shown in FIG. 3, the force-sensing structure 300 includes multiplelayers. In this example, the force-sensing structure includes an upperportion 310 and a lower portion 320 separated by a deformable middlebody or compressible element 330. The upper portion 310 includes anupper body 311 which may be formed from a layer of polyimide flexmaterial. The upper portion 310 also includes an upper capacitive plate312 formed from a layer of copper bonded to or deposited on the upperbody 311. Likewise, the lower portion 320 includes a lower body 321which may also be formed from a layer of polyimide flex material. Thelower portion 320 also includes a lower capacitive plate 322 formed froma layer of copper bonded to or deposited on the lower body 321. In thisexample, the polyimide flex material is approximately 0.05 millimetersthick. However, other thicknesses and other materials may be used toform the force-sensing structure 300.

As shown in FIG. 3, a capacitance (shown by the capacitor symbol) may beformed between the upper and lower capacitive plates 312, 322, which, inthis example, are separated by the compressible element 330. In thisexample, the compressible element 300 is formed from a silicone materialapproximately 0.2 millimeters thick with a tolerance of plus or minus0.09 millimeters. In other embodiments, the compressible element 300 maybe formed from a different material and have a different thickness.

The force-sensing structure 300 depicted in FIG. 3 can be used to detectand measure a user-applied force. For example, a user may press down onthe cover glass 104 (or on an upper surface of the electronic device100, in embodiments lacking a display and/or cover glass) to exert aforce on the device 100. The cover glass 104 may move downward inresponse to the force, compressing the compressible element 330 of theforce-sensing structure 300. In some cases, the compressible element 330becomes flattened by the compression resulting the in first and secondcapacitive plates 312, 322 moving closer together. As a result, thecapacitance between the first and second capacitive plates 312, 322 maychange. As previously mentioned, a change in capacitance may produce anelectrical signal or change in an electrical signal, which may bedetected and measured by associated circuitry and may be used toestimate the force exerted on the cover glass 104 by the user.

As shown in FIG. 3, the upper and lower capacitive plates 312, 322 mayextend outward from the upper and lower bodies 311, 321, respectively.That is, at certain locations along the length of the force-sensingstructure 300, a portion of the capacitive plates 312, 322 may be bareand exposed. The exposed portion of the capacitive plates may facilitateconnection to a wire, conduit, or other electrical connection and allowsignals to be communicated between the force-sensing structure 300 andassociated electronic circuitry in order to measure capacitance changesand estimate force.

In some embodiments, a second, auxiliary structure may be formed withinthe device 100 or within a segment of the force-sensing structure. Theauxiliary structure may also include an upper capacitive plate and alower capacitive plate separated by a compressible element. However, theauxiliary structure may not be configured to be compressed by the coverglass 104, and instead may serve as a reference capacitance used toaccount for changes in environmental conditions surrounding the device.For example, the elasticity and/or compressibility of the compressibleelement (e.g., a silicone material) may vary due to changes in theamount of absorbed moisture. In this case, it may be advantageous to usean auxiliary structure to measure (directly or indirectly) changes inthe physical properties of the compressible element to account forchanges in the moisture content. In one example, the auxiliary structuremay form a capacitor with the upper and lower capacitive platesseparated by a compressible element. The capacitor may be connected to asecond electrical circuit that monitors the capacitance between theplates of the auxiliary structure separately from any force-sensitivestructure. The auxiliary structure may be positioned in a part of thedevice such that it does not experience any (or very little) compressionwhen a user presses down on the cover glass but is still exposed to thesame or a similar environment as the force-sensing structure. Thus, anychanges in the capacitance between the plates of the auxiliary structuremay be purely due to absorbed moisture and/or aging of the compressibleelement (e.g., a silicone material). The output signal from theauxiliary structure may be used to adjust readings from force-sensitivestructure to compensate for changes in the environmental conditions thataffect the physical properties of the compressible element.

FIGS. 4 and 5 depict alternative embodiments of a force-sensitivestructure. Specifically, FIG. 4 depicts a force-sensitive structure 400having an upper portion 410 including an upper body 411 attached to anupper capacitive plate 412. The force-sensitive structure 400 alsoincludes a lower portion 420 including a lower body 421 attached to alower capacitive plate 422. The upper and lower portions 410, 420 areseparated by a compressible element 430 and form a capacitor that can beused to detect a force applied to the cover glass 104. In the exampledepicted in FIG. 4, the upper and lower capacitive plates 412, 422 donot extend beyond the upper and lower bodies 411, 421. In this case,electrical communication with the force-sensitive structure 400 may befacilitated by an electrical terminal or conduit located within theprofile of the force-sensitive structure 400.

FIG. 5 depicts another alternative embodiment of an electronic device100 incorporating a force-sensitive structure 500. In this embodiment,an environmental seal 550 may be positioned between the cover glass 104and the force-sensitive structure 500 to prevent ingress of moisture,dust, dirt, and other potential environmental contaminants. Theenvironmental seal 550 may be formed, for example, from an extrudedcompliant material, such as Buna rubber, Viton, EPDM, or the like. Insome cases, the environmental seal 550 is formed as a bead of sealantmaterial that cures after being applied to an element of the device 100.

Optionally, as shown in FIG. 5, the device may also include a support552 positioned between the seal 550 and the cover glass 104 to provide abonding surface for the environmental seal 550. In this example, thesupport 552 is attached to the cover glass 104 and, therefore, ismovable with respect to the enclosure 102. Thus, as a force is appliedto the cover glass 104, the cover glass 104, optional support 552, andseal 550 may all move downward to compress the force-sensing structure500. Thus, in the present embodiment, the seal 550 can be used toisolate the force-sensing structure 500 from moisture and externaldebris while still allowing operation force-sensing structure 500. Inaddition to or in place of the seal 550, the device 100 may also includeone or more wiping seals located between an edge of the cover glass 104and a portion of the enclosure 102. Furthermore, a baffle seal ormembrane may be installed between the cover glass 104 and a portion ofthe enclosure 102, the baffle seal configured to prevent contaminatesfrom entering the internal portion of the device 100.

In some embodiments, the environmental seal 550 is compliant and inother embodiments, the environmental seal 550 is not compliant and maybe rigid. A rigid seal may be advantageous by transmitting force to theforce-sensing structure 500 directly, while a compliant or flexible sealmay compress somewhat before transmitting any force. Either type of sealmay be used, although the output of the force-sensitive structure 500may be affected by compression of a flexible seal.

FIG. 6 depicts another alternative embodiment of a device having acapacitive force sensor. As shown in FIG. 6, a touch device case 605(e.g., housing) can be shaped and positioned to hold a cover glasselement 610. For example, the touch device case 605 can include arectilinear frame, such as having a shape of a picture frame, with thecover glass element 610 having the shape of a picture cover (as wouldoccur if a picture were placed below the cover glass element 610). Thetouch device case 605 can include a backing (not shown) or a midframeelement (not shown), which can stabilize the touch device case 605against bending, warping, or other physical distortion. The touch devicecase 605 can also define a space in which circuitry for the touch device(as described herein) can be positioned. This has the effect that thecircuitry for the touch device can be protected against foreigncontaminants or unwanted touching, and against bending or warping, orother electrical or physical effects that might possibly cause circuitryerrors or other problems for the touch device.

As shown in FIG. 6, the touch device case 605 can include an outer edge615, such as can be defined by an outer lip or a protrusion upward froma baseline of the touch device case 605, and which can be positioned toprevent excess slippage or other movement of the cover glass element 610in either an X or Y direction. In this context, a Z direction generallyindicates a direction substantially normal (likely to be at a 90 degreeangle, but this is not required) to a plane of the cover glass element610 and a top surface of the touch device, while the X and Y directionsgenerally indicate directions substantially within the same plane of thecover glass element 610 (likely to be at 90 degree angles with respectto each other, but this is not required).

As shown in FIG. 6, the cover glass element 610 and the outer edge 615define a cover glass gap 620 between them, with the effect that thecover glass element 610 does not bump or rub against the touch devicecase 605. In one embodiment, the touch device can include an optionalelastomer 625, or other substance, positioned between the cover glasselement 610 and the outer edge 615. This can have the effect ofproviding shock absorption in the event of a sudden acceleration of thecover glass element 610 in the direction of the outer edge 615, such asin the event the touch device is dropped, hit, kicked, or otherwisecatastrophically moved. For example, the elastomer 625 can be disposedaround the edges of the cover glass element 610, with the effect offorming an O-ring shape or similar shape. The elastomer 625 can alsohave the effect of preventing, or at least militating against, foreignobject damage that might be caused by dust or other objects slippingbetween the cover glass element 610 and the outer edge 615.

As shown in FIG. 6, the touch device case 605 includes a cover glassshelf 630, such as can be defined by an inner lip or internal protrusioninward from the outer edge 615 of the touch device case 605, and whichcan be positioned to support the cover glass element 610. For example,the cover glass element 610 can rest on the cover glass shelf 630, whichcan prevent the cover glass element 610 from slipping down into thecircuitry for the touch device. In alternative embodiments, the touchdevice case 605 can include a midframe (not shown), such as can bedefined by an internal support element positioned to support the coverglass element 610. For example, the midframe can include a relativelysolid (absent optional holes) element positioned to support at leastsome of the circuitry for the touch device.

As shown in FIG. 6, the device includes a force-sensing structure 600.In this example, the force-sensing structure 600 includes a first upperportion comprising a first pressure sensitive adhesive (PSA) layer 635,having a thickness of about 100 microns and a first flex circuit 640.The first flex circuit 640 includes a set of drive/sense linesconfigured to conduct electric signals and/or act a capacitive plate.The force-sensing structure 600 also includes a lower portion comprisinga second PSA layer 645, such as also having a thickness of about 100microns, and a second flex circuit 650 also having conductivedrive/sense lines for conducting signals and acting as a capacitiveplate. The first flex circuit 640 and the second flex circuit 650 areconfigured to operate in response to control by the drive/sense linesand can form a capacitive sensor. As explained above with respect toprevious embodiments, changes in the capacitance between the upper andlower portions of the force-sensing structure 600 may be related to anamount of deflection or change in distance between the first flexcircuit 640 and the second flex circuit 650. (In other embodiments, oneor more strain gauges can be used instead of a capacitive sensor.) Inone example, if the cover glass element 610 is tilted (such as bypressure or other applied force), the first flex circuit 640 and thesecond flex circuit 650 can become closer or become farther away,depending on location with respect to the axis and location of tilt. Asfurther described herein, the first flex circuit 640 and the second flexcircuit 650 can be replicated in several locations on the touch devicecase 605.

The force-sensing structure 600 is typically operatively connected to aforce-sensing circuit configured to detect and measure changes incapacitance. By measuring changes in capacitance, the force-sensingcircuit can be used to estimate relative displacement of one or moreforce-sensing structures which, in turn can be used to determine an axisand location of tilt of the cover glass element 610. Furthermore, thechanges in capacitance can be used to estimate a force applied to thecover glass element 610. In some embodiments, the force-sensing circuitincludes or is coupled to a processor.

In one embodiment, a region between the first flex circuit 640 and thesecond flex circuit 650 can define a substantially empty space (that is,filled with air). In alternative embodiments, the region between thefirst flex circuit 640 and the second flex circuit 650 can include acompressible layer 655. For a first example, the space between the firstand second flex circuits 640, 650 can include a set of spring elementsinterspersed within the space. In this case, the first flex circuit 640and the second flex circuit 650 are held apart by spring forces and donot generally touch. For a second example, the compressible layer 655can include a microstructure constructed at least in part from silicone,such as a set of silicone pyramids or a set of silicone springs, alsowith the effect that the first flex circuit 640 and the second flexcircuit 650 are held apart by a spring force and do not generally touch.

As described generally above, the cover glass element 610 may include atransparent touch sensor that is configured to detect the location ofone or more touches. As mentioned previously, the transparent touchsensor may be formed from one or more arrays of transparent conductivelines coupled to touch sensor circuitry. Types of transparent touchsensors that may be integrated into the cover glass element 610,include, without limitation, mutual capacitive sensors, self-capacitivetouch sensors, and resistive touch sensors.

In one embodiment, an area of the cover glass element 610 above thefirst flex circuit 640 and the second flex circuit 650 can be coveredwith an ink mask 660. In one embodiment, the ink mask 660 is disposedbelow the cover glass element 610 and above the first flex circuit 640.This has the effect that a user of the touch device does not generallysee either the first flex circuit 640 or the second flex circuit 650, orany of the elements coupling them to the touch device case 605, thecover glass element 610, or any circuits for touch device (not shown).For example, the touch device can include a surface 665, which caninclude a surface of the cover glass element 610 in places where the inkmask 660 is absent, and can include a surface of the ink mask where theink mask 660 is present. As described above, a Z direction 670 canindicate a direction substantially normal to the surface 665 of thetouch device.

In one embodiment, the interaction between the cover glass element 610and the outer edge 615 may result in a set of forces at the outer edgeof the cover glass element 610. In some embodiments, a force-sensingstructure 600 (or alternatively a strain gauge) is placed at two or moreedges of the cover glass element 610. Each of the two or moreforce-sensing structures may be operatively coupled to force-sensingcircuitry in the touch device and can be used to detect and measurethese forces. Additionally, by estimating the relative displacement ineach of the two or more force-sensing structures, the circuit can beused to determine a normal vector to the cover glass element 610 thatrepresents a location of applied force (that is, a location of thenormal vector) as well as an amount applied force (that is, a magnitudeof the normal vector).

In one embodiment, the normal vector can be determined in response to anamount of tilt of the cover glass element or an amount of pressure at aX and the Y location. For example, a set of displacements can bemeasured using two or more force-sensing structures located at one ormore edges on the perimeter of the cover glass element. In oneembodiment, the displacements are proportional or can be correlated toone or more applied forces. A total force Fz can be determined inresponse to the individual forces at the edges of the cover glasselement, and a centroid location (x0, y0) can be determined based on acorrelation between the individual forces. Thus, using two or moreforce-sensing structures, a total force Fz and central location (x0, y0)can be computed that correlates to the actual force exerted on the coverglass element. Additionally, signals generated by multiple force-sensingstructures can be coupled with the output of a touch sensor (potentiallyintegrated into the cover glass elements) to resolve both the location amagnitude (applied force) for multiple finger touches on a cover glasselement.

FIG. 7 depicts another exemplary embodiment of a device having acapacitive force sensor. The device may include a touch-sensitive region710, which may (or may not) coincide with a display region such as anLED, LCD or OLED display. In this example, the touch-sensitive region710 is formed from a transparent touch sensor integrated with the coverglass element 610.

FIG. 7 depicts, the touch device as viewed from above and includes thetouch device case 605, the cover glass element 610, and the outer edge615. The touch device also includes a home button 705, and atouch-sensitive region 710 (in which the touch device can determine alocation of one or more touches using, for example, a capacitive touchsensor). The home button 705 may be partially or fully within thetouch-sensitive region 710, or may be located outside thetouch-sensitive region 710.

In one embodiment, the shape of the touch device can be indicated by apair of centerlines 715, such as an X direction centerline 715 x and a Ydirection centerline 715 y. The touch device can include, along one ormore edges, such as bordering the touch-sensitive region 710, a set offorce sensors 700. The force sensors 700 may be formed from one or morecapacitive force sensors similar to those as described with respect toFIGS. 3-6. Alternatively, the force sensors 700 may include otherdevices capable of sensing applied force, such as a strain gauge.

As shown in FIG. 7, a device may include a plurality of force sensors700 located along one or more edges of the perimeter of thetouch-sensitive region 710. Each force sensor 700 includes at least twocapacitive plates separated by a compressible intermediate layer. In oneembodiment, the set of force sensors 700 can be disposed substantiallyoutside a transparent portion of the touch-sensitive region 710. Forexample, the force sensors 700 may be located under an ink mask 660(such as similar to or like that described with reference to the FIG.6). In such cases, the force sensors 700 can be positioned with a gaugespacing 725 between pairs of the force sensors 700, and with an edgespacing 730 between individual ones of the force sensors 700 and an edgethe touch device. In alternative embodiments, the force sensors 700 maybe positioned beneath a display stack or located in another positionwith respect to the touch-sensitive region 710. The force sensors 700may be evenly spaced from one another, spaced at uneven intervals, atrepeating intervals, or as necessary Likewise, the force sensors 700 maybe positioned along all sides of the touch-sensitive region 710, atcorners of the device, along less than all sides of the touch-sensitiveregion 710, or along a single edge of the touch-sensitive region 710.Accordingly, the sensor distribution shown in FIG. 7 is meant to be asample, partial distribution and not limiting.

In one embodiment, each force sensor 700 is coupled to force-sensingcircuitry that is configured to measure an amount of capacitance betweena first flex circuit and a second flex circuit, which may be correlatedto estimate a distance between the first flex circuit and the secondflex circuit. The relative position of the first and second flexcircuits may be similar to the configuration depicted in FIG. 6,discussed above. Similar to embodiments described above, an amount ofcapacitance between the first sensing element defined on the first flexcircuit and the second sensing element defined on the second flexcircuit can be detected and measured using force detection circuitry,which may include a processor. In such cases, the amount of appliedforce can be correlated to a relative change in distance between thefirst flex circuit and the second flex circuit, relative to a restposition when there is no force applied to the cover glass element 610.It should be appreciated that each force sensor 700 may be formed fromfirst and second flex circuits, or may be a separate element.

In an alternative embodiment, each force sensor 700 is coupled toforce-sensing circuitry that is configured to measure an amount ofresistance between the first flex circuit and the second flex circuit.For example, the first and second flex circuits may be coupled byresistive layer. By measuring the resistance or change in resistance,the force-sensing circuitry can be used to determine a distance betweenthe first flex circuit and the second flex circuit. For example, anamount of resistance between the first flex circuit and the second flexcircuit can be correlated to a distance between the first flex circuitand the second flex circuit. This may occur when, for example thecompressible, resistive layer is formed from a material that has avariable resistivity dependent on its thickness or an amount ofcompression. In one such case, the compressible, resistive layerincludes a microstructure that has a resistance that increases like aspring force, similar to a strain gauge. The force-sensing circuitry mayestimate the distance between the flex circuits by measuring theresistance or changes to the resistance in the compressible, resistivelayer.

With reference to FIG. 7, the force sensors 700 can be operativelycoupled to force-sensing circuitry (including a processor) that isconfigured to determine a set of distances (at distinct locations alongthe edge of the cover glass element 110) corresponding to the set offorce sensors 700. That is, the force-sensing circuitry can estimate thedistance between the first flex circuit and the second flex circuitbased on the measured capacitance at each force sensor. In oneembodiment, the displacements at each sensor 700 correlate to appliedforces at the locations of those force sensors 700. Similar to thetechnique described above with respect to FIG. 6, a total force Fz canbe determined based on an estimate of the individual forces, and acentroid location (x0, y0) can be determined based on a weighting of theestimate of the individual forces. In one embodiment, the total force Fzand the centroid location (x0, y0) is calibrated such that a set ofcomputed forces and moments in response to the values of the total forceFz and the centroid location (x0, y0) best matches the observed valuesfor displacements and forces at each of the set of force sensors 700.Thus, using multiple force sensors, a total force Fz and centrallocation (x0, y0) can be computed that correlates to the actual forceexerted on the device. Additionally, signals generated by multiple forcesensors can be coupled with the output of a touch sensor (potentiallyintegrated into the cover glass elements) to resolve both the locationsand magnitudes (due to applied forces) for multiple finger touches onthe device.

FIG. 8 depicts another exemplary embodiment of a device having acapacitive force sensor. In particular, the device depicted in FIG. 8includes a cover glass element that is deformable.

As shown in FIG. 8, a cover glass element 805 can be coupled to a frameelement 810, which can be coupled to a touch device frame 815. In oneembodiment, there is a spatial separation between the cover glasselement 805 and the frame element 810. For a first example, the coverglass element 805 can have a thickness of about 0.90 mm, although thisparticular thickness is merely exemplary and is not required. For asecond example, the frame element 810 can include an elastomer, aplastic, or include construction from other substances. The cover glasselement 805 can also be positioned above a display stack 820, such as adisplay stack from a touch device and adapted to provide a graphical ortext display.

In one embodiment, the display stack 820 can be positioned above areflector sheet 825 including an electrode pattern, such as can be usedfor drive and sense lines in a rectilinear capacitive array orindividual sensor structures in an array. The reflector sheet 825 can bepositioned above an air gap 830, such as can be used for capacitancebetween the reflector sheet 825 and another element. For example, theair gap 830 can have a thickness of about 0.10 mm, although thisparticular thickness is merely exemplary and is not required.

In one embodiment, the air gap 830 can be positioned above a circuit 835having capacitive traces or elements, which may include a set of driveand sense traces/elements or be formed from an array of individualsensing traces/elements. For example, the circuit 835 can have athickness of about 0.10 mm, although this particular thickness is merelyexemplary and is not required.

In one embodiment, the circuit 835 can be positioned above a pressuresensitive adhesive (PSA) element 840. For example, the PSA element 840can have a thickness of about 0.03 mm, although this particularthickness is merely exemplary and is not required. Further, a primer maybe used between PSA and the housing to affix the structure to thehousing. The structure may be optically aligned with the housing priorto bonding.

In one embodiment, the PSA element 840 can be positioned above amidplate element 845. For a first example, the midplate element 845 canhave a thickness of about 0.25 mm, although this particular thickness ismerely exemplary and is not required. For a second example, the midplateelement 845 can be supportive of the elements coupled thereto and belowthe air gap 830.

In one embodiment, the cover glass element 805, the display stack 820,and related elements can be relatively deformable. This can have theeffect that applied force to the surface of the touch device can cause achange in distance between elements near the air gap 830, and a changein measured capacitance by circuits positioned near the air gap 830. Forexample, a set of drive and sense lines, or an array of individualsensing elements, could be positioned in the reflector sheet 825 or inthe circuit 835, can measure a capacitance across the air gap 830.

In such cases, the capacitance across the air gap 830 would be subjectto change in response to deformation of the cover glass element 805, thedisplay stack 820, and related elements. This would have the effect thatelements positioned near the air gap 830 would be able to measure thechange in capacitance, and would be able to determine an amount ormagnitude of an applied force in response thereto.

In some embodiments, multiple force sensors may be formed over the areaof the cover glass element 805. In one embodiment, the set of forcesensors can be positioned in a rectilinear array, such as an array inwhich each one of the force sensors is positioned at an [X, Y] locationover the area of the cover glass element 805. For example, each one ofthe force sensors can include a capacitive force sensor exhibitingmutual capacitance between drive and sensor elements, or exhibitingself-capacitance. In another example, each one of the sensors caninclude a resistive strain gauge exhibiting a change in resistance inresponse to applied force, such as a resistive strain gauge as describedwith respect to FIG. 6, above.

In one embodiment, the applied force can affect each force sensor thatis substantially near the applied force. The applied force affects eachsuch force sensor differently depending on an amount of the appliedforce and a distance between the [X, Y] location of the applied forceand the [X, Y] location of the affected force sensor. This has theeffect that a processor or other circuit in the touch device candetermine a mapping of applied force, and in response thereto, a set of[X, Y] locations and a Z displacement of the cover glass element 805.For example, particular Z displacement of points along the edges of thecover glass element 805 (or within a touch-sensitive region) can be usedto determine the [X, Y] location of the applied force. In oneembodiment, the cover glass element 805 may be approximately 700 micronsthick, although this thickness may vary between embodiments.

In one embodiment, the same or similar information can be used todetermine the [X, Y] location and Z displacement of more than one suchapplied force. In such cases where multiple forces are applied, aprocessor or other circuit in the touch device can determine a centroidof applied force, from which the touch device can determine one or moreindividual forces. For example, from this information, a processor orother circuit can determine one or more [X, Y] locations where force isbeing applied, and an amount or magnitude of force being applied at eachsuch location.

In one embodiment, the interaction between the cover glass element 805and the air gap 830 defines a set of forces at each location of appliedforce. A processor or other circuit in the touch device can measurethese forces, such as using one or more capacitive sensing elements (asdescribed herein) or using one or more strain gauges, distributed atlocations throughout cover glass element 805. In response to thoseforces, the circuit can determine a set of normal vectors to the coverglass element 805 representing one or more locations of applied forceand one or more amounts or magnitudes of the applied force.

In one embodiment, the locations of applied force can be determined inresponse to the distribution of sensed applied force at each location onthe cover glass element 805, as described above, at each of the X andthe Y locations, thus assigning each such location a Z amount of appliedforce. For a first example, a total centroid of applied force can bedetermined in response to the distribution of sensed applied force. Theprocessor or other circuit can then locate each individual likelyapplied force, identify its amount of force, and subtract out thatidentified force from the sensed applied force at each location. Thiscan have the effect of providing the processor or other circuit with away to identify each applied force individually, until all suchindividual applied forces have been found.

In one embodiment, an amount or magnitude of force can be determined ateach of a set of distinct locations at which a distinct force sensor isdisposed below the cover glass element 805. For example, in oneembodiment, the force sensors can be disposed in a grid below the coverglass element 805. Having the amount of force at each such location, aweighted centroid of that set of force amounts can be computed using aweighted sum of the locations at which each applied force is measured.Having determined such a centroid, the processor can determine a nearestlocal maximum force, either in response to the nearest maximum forcesensor, or in response to a touch location sensor, or both. Havingdetermined a nearest local maximum force, the processor can subtractthat force and its expected effect on each force sensor, and repeat theprocess until each individual applied force is determined. Inalternative embodiments, other and further techniques could be used inaddition or instead.

-   -   4. Force-Sensitive Device System

FIG. 9 depicts an exemplary communication between a touch I/O device anda computing system. In this example, the touch I/O device 901 includesone or more sensors for detecting a touch by an operator or user. Thetouch device 901 transmits electronic signals from the one or moresensors to a computing system 903 over a communication channel 902. Anexample computing system 903 is described below with respect to FIG. 10and includes one or more computer processors and computer-readablememory for storing computer-executable instructions. The touch I/Odevice, communication channel 902 and computing system 903 may all beintegrated together as a part of the same touch device.

As shown in FIG. 9, embodiments may include touch I/O device 901 thatcan receive touch input and force input (such as possibly includingtouch locations and applied force at those locations) for interactingwith computing system 903 via wired or wireless communication channel902. Touch I/O device 901 may be used to provide user input to computingsystem 903 in lieu of or in combination with other input devices such asa keyboard, mouse, or possibly other devices. In alternativeembodiments, touch I/O device 901 may be used in conjunction with otherinput devices, such as in addition to or in lieu of a mouse, trackpad,or possibly another pointing device. One or more touch I/O devices 901may be used for providing user input to computing system 903. Touch I/Odevice 901 may be an integral part of computing system 903 (e.g., touchscreen on a laptop) or may be separate from computing system 903.

Touch I/O device 901 may include a touch sensitive and/or forcesensitive panel which is wholly or partially transparent,semitransparent, non-transparent, opaque or any combination thereof.Touch I/O device 901 may be embodied as a touch screen, touch pad, atouch screen functioning as a touch pad (e.g., a touch screen replacingthe touchpad of a laptop), a touch screen or touchpad combined orincorporated with any other input device (e.g., a touch screen ortouchpad disposed on a keyboard, disposed on a trackpad or otherpointing device), any multi-dimensional object having a touch sensitivesurface for receiving touch input, or another type of input device orinput/output device.

In one example, touch I/O device 901 is a touch screen that may includea transparent and/or semitransparent touch-sensitive and force-sensitivepanel at least partially or wholly positioned over at least a portion ofa display. (Although, the touch sensitive and force sensitive panel isdescribed as at least partially or wholly positioned over at least aportion of a display, in alternative embodiments, at least a portion ofcircuitry or other elements used in embodiments of the touch sensitiveand force sensitive panel may be at least positioned partially or whollypositioned under at least a portion of a display, interleaved withcircuits used with at least a portion of a display, or otherwise.)According to this embodiment, touch I/O device 901 functions to displaygraphical data transmitted from computing system 903 (and/or anothersource) and also functions to receive user input. In other embodiments,touch I/O device 901 may be embodied as an integrated touch screen wheretouch sensitive and force sensitive components/devices are integral withdisplay components/devices. In still other embodiments a touch screenmay be used as a supplemental or additional display screen fordisplaying supplemental or the same graphical data as a primary displayand to receive touch input, including possibly touch locations andapplied force at those locations.

Touch I/O device 901 may be configured to detect the location of one ormore touches or near touches on device 901, and where applicable, forceof those touches, based on capacitive, resistive, optical, acoustic,inductive, mechanical, chemical, or electromagnetic measurements, inlieu of or in combination or conjunction with any phenomena that can bemeasured with respect to the occurrences of the one or more touches ornear touches, and where applicable, force of those touches, in proximityto the touch I/O device 901. Software, hardware, firmware or anycombination thereof may be used to process the measurements of thedetected touches, and where applicable, force of those touches, toidentify and track one or more gestures. A gesture may correspond tostationary or non-stationary, single or multiple, touches or neartouches, and where applicable, force of those touches, on touch I/Odevice 901. A gesture may be performed by moving one or more fingers orother objects in a particular manner on touch I/O device 901 such astapping, pressing, rocking, scrubbing, twisting, changing orientation,pressing with varying pressure and the like at essentially the sametime, contiguously, consecutively, or otherwise. A gesture may becharacterized by, but is not limited to a pinching, sliding, swiping,rotating, flexing, dragging, tapping, pushing and/or releasing, or othermotion between or with any other finger or fingers, or any other portionof the body or other object. A single gesture may be performed with oneor more hands, or any other portion of the body or other object by oneor more users, or any combination thereof.

Computing system 903 may drive a display with graphical data to displaya graphical user interface (GUI). The GUI may be configured to receivetouch input, and where applicable, force of that touch input, via touchI/O device 901. Embodied as a touch screen, touch I/O device 901 maydisplay the GUI. Alternatively, the GUI may be displayed on a displayseparate from touch I/O device 901. The GUI may include graphicalelements displayed at particular locations within the interface.Graphical elements may include but are not limited to a variety ofdisplayed virtual input devices including virtual scroll wheels, avirtual keyboard, virtual knobs or dials, virtual buttons, virtuallevers, any virtual UI, and the like. A user may perform gestures at oneor more particular locations on touch I/O device 901 which may beassociated with the graphical elements of the GUI. In other embodiments,the user may perform gestures at one or more locations that areindependent of the locations of graphical elements of the GUI. Gesturesperformed on touch I/O device 901 may directly or indirectly manipulate,control, modify, move, actuate, initiate, or generally affect graphicalelements such as cursors, icons, media files, lists, text, all orportions of images, or the like within the GUI. For instance, in thecase of a touch screen, a user may directly interact with a graphicalelement by performing a gesture over the graphical element on the touchscreen. Alternatively, a touch pad generally provides indirectinteraction. Gestures may also affect non-displayed GUI elements (e.g.,causing user interfaces to appear) or may affect other actions withincomputing system 903 (e.g., affect a state or mode of a GUI,application, or operating system). Gestures may or may not be performedon touch I/O device 901 in conjunction with a displayed cursor. Forinstance, in the case in which gestures are performed on a touchpad, acursor (or pointer) may be displayed on a display screen or touch screenand the cursor may be controlled via touch input, and where applicable,force of that touch input, on the touchpad to interact with graphicalobjects on the display screen. In other embodiments in which gesturesare performed directly on a touch screen, a user may interact directlywith objects on the touch screen, with or without a cursor or pointerbeing displayed on the touch screen.

Feedback may be provided to the user via communication channel 902 inresponse to or based on the touch or near touches, and where applicable,force of those touches, on touch I/O device 901. Feedback may betransmitted optically, mechanically, electrically, olfactory,acoustically, haptically, or the like or any combination thereof and ina variable or non-variable manner.

As previously mentioned, the touch I/O device, communication channel902, and the computing system 903 may all be integrated into a touchdevice or other system. The touch device or system may be a portable ornon-portable device, including, but not limited to, a communicationdevice (e.g., mobile phone, smart phone), a multi-media device (e.g.,MP3 player, TV, radio), a portable or handheld computer (e.g., tablet,netbook, laptop), a desktop computer, an all-in-one desktop, aperipheral device, or any other (portable or non-portable) system ordevice adaptable to the inclusion of system architecture depicted inFIG. 10, including combinations of two or more of these types ofdevices.

FIG. 10 depicts a block diagram of one embodiment of system 1000 thatgenerally includes one or more computer-readable media 1001, processingsystem 1004, Input/Output (I/O) subsystem 1006, electromagneticfrequency circuitry, such as possibly radio frequency (RF) or otherfrequency circuitry 1008 and audio circuitry 1010. These components maybe coupled by one or more communication buses or signal lines 1003. Eachsuch bus or signal line may be denoted in the form 1003-X, where X canbe a unique number. The bus or signal line may carry data of theappropriate type between components; each bus or signal line may differfrom other buses/lines, but may perform generally similar operations.

It should be apparent that the architecture shown in FIG. 10 is only oneexample architecture of system 1000, and that system 1000 could havemore or fewer components than shown, or a different configuration ofcomponents. The various components shown in FIG. 10 can be implementedin hardware, software, firmware or any combination thereof, includingone or more signal processing and/or application specific integratedcircuits.

Shown in FIG. 10, RF circuitry 1008 is used to send and receiveinformation over a wireless link or network to one or more other devicesand includes well-known circuitry for performing this function. RFcircuitry 1008 and audio circuitry 1010 are coupled to processing system1004 via peripherals interface 1016. Interface 1016 includes variousknown components for establishing and maintaining communication betweenperipherals and processing system 1004. Audio circuitry 1010 is coupledto audio speaker 1050 and microphone 1052 and includes known circuitryfor processing voice signals received from interface 1016 to enable auser to communicate in real-time with other users. In some embodiments,audio circuitry 1010 includes a headphone jack (not shown).

Peripherals interface 1016 couples the input and output peripherals ofthe system to processor 1018 and computer-readable medium 1001. One ormore processors 1018 communicate with one or more computer-readablemedia 1001 via controller 1020. Computer-readable medium 1001 can be anydevice or medium that can store code and/or data for use by one or moreprocessors 1018. Medium 1001 can include a memory hierarchy, includingbut not limited to cache, main memory and secondary memory. The memoryhierarchy can be implemented using any combination of RAM (e.g., SRAM,DRAM, DDRAM), ROM, FLASH, magnetic and/or optical storage devices, suchas disk drives, magnetic tape, CDs (compact disks) and DVDs (digitalvideo discs). Medium 1001 may also include a transmission medium forcarrying information-bearing signals indicative of computer instructionsor data (with or without a carrier wave upon which the signals aremodulated). For example, the transmission medium may include acommunications network, including but not limited to the Internet (alsoreferred to as the World Wide Web), intranet(s), Local Area Networks(LANs), Wide Local Area Networks (WLANs), Storage Area Networks (SANs),Metropolitan Area Networks (MAN) and the like.

One or more processors 1018 run various software components stored onmedium 1001 to perform various functions for system 1000. In someembodiments, the software components include operating system 1022,communication module (or set of instructions) 1024, touch and appliedforce processing module (or set of instructions) 1026, graphics module(or set of instructions) 1028, and one or more applications (or set ofinstructions) 1030. Each of these modules and above noted applicationscorrespond to a set of instructions for performing one or more functionsdescribed above and the methods described in this application (e.g., thecomputer-implemented methods and other information processing methodsdescribed herein). These modules (i.e., sets of instructions) need notbe implemented as separate software programs, procedures or modules, andthus various subsets of these modules may be combined or otherwiserearranged in various embodiments. In some embodiments, medium 1001 maystore a subset of the modules and data structures identified above.Furthermore, medium 1001 may store additional modules and datastructures not described above.

Operating system 1022 includes various procedures, sets of instructions,software components and/or drivers for controlling and managing generalsystem tasks (e.g., memory management, storage device control, powermanagement, etc.) and facilitates communication between various hardwareand software components.

Communication module 1024 facilitates communication with other devicesover one or more external ports 1036 or via RF circuitry 1008 andincludes various software components for handling data received from RFcircuitry 1008 and/or external port 1036.

Graphics module 1028 includes various known software components forrendering, animating and displaying graphical objects on a displaysurface. In embodiments in which touch I/O device 1012 is a touchsensitive and force sensitive display (e.g., touch screen), graphicsmodule 1028 includes components for rendering, displaying, and animatingobjects on the touch sensitive and force sensitive display.

One or more applications 1030 can include any applications installed onsystem 1000, including without limitation, a browser, address book,contact list, email, instant messaging, word processing, keyboardemulation, widgets, JAVA-enabled applications, encryption, digitalrights management, voice recognition, voice replication, locationdetermination capability (such as that provided by the globalpositioning system, also sometimes referred to herein as “GPS”), a musicplayer, and otherwise.

Touch processing module 1026 includes various software components forperforming various tasks associated with touch I/O device 1012 includingbut not limited to receiving and processing touch input and appliedforce input received from I/O device 1012 via touch I/O devicecontroller 1032. In some cases, the touch processing module 1026includes computer instructions for operating the force sensor 1060. Forexample, the touch processing module 1026 may include instructions forperforming one or more operations described below with respect toprocesses 1100 and 1150 of FIGS. 11A-B. In some cases, the touchprocessing module 1026 includes parameters or settings that may beimplemented in the operation of the force sensor 1060.

I/O subsystem 1006 is coupled to touch I/O device 1012 and one or moreother I/O devices 1014 for controlling or performing various functions.Touch I/O device 1012 communicates with processing system 1004 via touchI/O device controller 1032, which includes various components forprocessing user touch input and applied force input (e.g., scanninghardware). One or more other input controllers 1034 receives/sendselectrical signals from/to other I/O devices 1014. Other I/O devices1014 may include physical buttons, dials, slider switches, sticks,keyboards, touch pads, additional display screens, or any combinationthereof.

If embodied as a touch screen, touch I/O device 1012 displays visualoutput to the user in a GUI. The visual output may include text,graphics, video, and any combination thereof. Some or all of the visualoutput may correspond to user-interface objects. Touch I/O device 1012forms a touch-sensitive and force-sensitive surface that accepts touchinput and applied force input from the user. Touch I/O device 1012 andtouch screen controller 1032 (along with any associated modules and/orsets of instructions in medium 1001) detects and tracks touches or neartouches, and where applicable, force of those touches (and any movementor release of the touch, and any change in the force of the touch) ontouch I/O device 1012 and converts the detected touch input and appliedforce input into interaction with graphical objects, such as one or moreuser-interface objects. In the case in which device 1012 is embodied asa touch screen, the user can directly interact with graphical objectsthat are displayed on the touch screen. Alternatively, in the case inwhich device 1012 is embodied as a touch device other than a touchscreen (e.g., a touch pad or trackpad), the user may indirectly interactwith graphical objects that are displayed on a separate display screenembodied as another I/O device 1014.

In embodiments in which touch I/O device 1012 is a touch screen, thetouch screen may use LCD (liquid crystal display) technology, LPD (lightemitting polymer display) technology, OLED (organic LED), or OEL(organic electro luminescence), although other display technologies maybe used in other embodiments.

Feedback may be provided by touch I/O device 2012 based on the user'stouch, and applied force, input as well as a state or states of what isbeing displayed and/or of the computing system. Feedback may betransmitted optically (e.g., light signal or displayed image),mechanically (e.g., haptic feedback, touch feedback, force feedback, orthe like), electrically (e.g., electrical stimulation), olfactory,acoustically (e.g., beep or the like), or the like or any combinationthereof and in a variable or non-variable manner.

System 1000 also includes power system 1044 for powering the varioushardware components and may include a power management system, one ormore power sources, a recharging system, a power failure detectioncircuit, a power converter or inverter, a power status indicator and anyother components typically associated with the generation, managementand distribution of power in portable devices.

In some embodiments, peripherals interface 1016, one or more processors1018, and memory controller 1020 may be implemented on a single chip,such as processing system 1004. In some other embodiments, they may beimplemented on separate chips.

In one embodiment, an example system includes a force sensor 1060integrated with the touch I/O device 2012. The force sensor 1060 mayinclude one or more of the force-sensitive structures described abovewith respect to any one of the example embodiments. Generally, the forcesensor 1060 is configured to generate an electronic signal or responsethat can be interpreted or processed as a magnitude of force of a touchon touch O/I device 1012. In some cases, the force sensor 1060 transmitselectronic signals directly to the touch I/O device via signal line1003-10. The signals may be relayed to the force sensor controller 1061in the I/O subsystem 1006. In some cases, the force sensor 1060transmits signals directly to the force sensor controller 1061 viasignal line 1003-11 without passing through the touch I/O device 1012.

The force sensor controller 1061 either alone or in combination with oneor more of the processors (e.g., processor 1018 or secure processor1040) may serve as the force sensing circuitry for the force sensor1060. In particular, the force sensor controller 1061 can be coupled toa processor or other computing device, such as the processor 1018 or thesecure processor 1040. In one example, the force sensor controller 1061is configured to calculate and estimated force based on electronicsignals generated by the force sensor 1060. Data regarding estimatedforce may be transmitted to the processor 1018 or secure processor 1040for use with other aspects of the system 1000, such as the touchprocessing module 1026. In one example, the force sensor controller 1061performs signal processing on the electronic signal that is produced bythe force sensor 1060, including, for example, analog to digitalconversion, filtering, and sampling operations. In some cases, otherprocessors in the system 1000 (e.g., processor 1018 or secure processor1040) that calculate an estimated force based on the processed signal.As a result, the system 1000 can utilize signals or data produced by theforce sensor controller 1061, which can be measured, calculated,computed, or otherwise manipulated. In one embodiment, the output of theforce sensor 1060 is used by one or more processors or other computingdevices, coupled to or accessible to the force sense controller 1061 orthe touch I/O device, such as the processor 1018, the secure processor1040, or otherwise. Additionally, output from the force sensor 1060 canbe used by one or more analog circuits or other specialized circuits,coupled to or accessible to the force sensor controller 1061 or thetouch I/O device 1012.

After reading this application, those skilled in the art would recognizethat techniques for obtaining information with respect to applied forceand contact on a touch I/O device, and using that associated informationto determine the magnitude and locations of applied force and contact ona touch I/O device, is responsive to, and transformative of, real-worlddata such as attenuated reflection and capacitive sensor data receivedfrom applied force or contact by a user's finger, and provides a usefuland tangible result in the service of detecting and using applied forceand contact with a touch I/O device. Moreover, after reading thisapplication, those skilled in the art would recognize that processing ofapplied force and contact sensor information by a computing deviceincludes substantial computer control and programming, involvessubstantial records of applied force and contact sensor information, andinvolves interaction with applied force and contact sensor hardware andoptionally a user interface for use of applied force and contact sensorinformation.

Certain aspects of the embodiments described in the present disclosuremay be provided as a computer program product, or software, that mayinclude, for example, a computer-readable storage medium or anon-transitory machine-readable medium having stored thereoninstructions, which may be used to program a computer system (or otherelectronic devices) to perform a process according to the presentdisclosure. A non-transitory machine-readable medium includes anymechanism for storing information in a form (e.g., software, processingapplication) readable by a machine (e.g., a computer). Thenon-transitory machine-readable medium may take the form of, but is notlimited to, a magnetic storage medium (e.g., floppy diskette, videocassette, and so on); optical storage medium (e.g., CD-ROM);magneto-optical storage medium; read only memory (ROM); random accessmemory (RAM); erasable programmable memory (e.g., EPROM and EEPROM);flash memory; and so on.

While the present disclosure has been described with reference tovarious embodiments, it will be understood that these embodiments areillustrative and that the scope of the disclosure is not limited tothem. Many variations, modifications, additions, and improvements arepossible. More generally, embodiments in accordance with the presentdisclosure have been described in the context of particular embodiments.Functionality may be separated or combined in procedures differently invarious embodiments of the disclosure or described with differentterminology. These and other variations, modifications, additions, andimprovements may fall within the scope of the disclosure as defined inthe claims that follow.

-   -   5. Methods of Operation

FIG. 11A depicts an exemplary process for operating a device having aforce sensor. The process may be applied using the force sensorsdescribed above with respect to FIGS. 2A, 2B, 3-8, discussed above.

FIG. 11A depicts an exemplary flow chart for a process 1100 thatincludes flow points and operational steps or functions. Although theseflow points and operations are shown in a particular order, in thecontext of a more generalized technique, there is no particularrequirement that the order of the operations must be followed as shown.For example, the flow points and operations could be performed in adifferent order, concurrently, in parallel, or otherwise. Similarly,although these flow points and operations are shown performed by ageneral purpose processor in a device, in the context of a moregeneralized approach, there is no particular requirement for any suchlimitation. For example, one or more such operations could be performedby a special purpose processor, by another circuit, or be offloaded toother processors or other circuits in other devices, such as byoffloading those functions to nearby devices using wireless technologyor by offloading those functions to cloud computing functions. In somecases, prior to performing the operations of process 1100, theelectronic device has been turned on and the operating system has beenloaded and is running. Also, the relevant hardware including, forexample, touch screen sensors, display devices, and force sensor devicesmay have been powered and may have been initialized.

At operation 1105, a force is applied to a location [X, Y] on the coverglass of the device. The force may be applied using either a finger orother pointing devices, such as a stylus or pen. In some cases, multipletouches may be applied to the cover glass of the device. For example, amulti-touch gesture or command may be input on the cover glass resultingin a net applied force.

At operation 1110, an electrical signal is detected and measured inresponse to the applied force. In one example, force-sensing circuit(which may include a processor) in the device measures a value from oneor more force sensors in response to the applied force. In oneembodiment, as described above with respect to FIGS. 2A, 2B, and 3-5, aforce-sensing circuit detects a change in the capacitance at one or moreforce-sensing structures. The change in capacitance may be correlated orused to estimate a deflection in the cover glass resulting from theapplied force. In another embodiment, as described with respect to FIG.6, the force-sensing circuit estimates an amount of tilt applied to thecover glass based on a signal or signals received from one or more forcesensors. In yet another embodiment, as described with respect to FIG. 7,the force-sensing circuit is used to detect a change in capacitancebetween capacitive sensors (or with respect to a single sensor, in aself-capacitance mode) at a set of distinct locations below the coverglass. The change in capacitance can be used to estimate thedisplacement on the cover glass resulting from the applied force.

At operation 1115, the location of the one or more touches isdetermined. In one example, the force-sensing circuit determines one ormore locations at which the force is being applied to the cover glasselement based on the signal or signals received from one or more forcesensors. The location may be determined by, for example, comparing theoutput from multiple force sensors and using the output to triangulateor estimate a location of the applied force.

At operation 1120, the amount or magnitude of the force being applied ateach location is estimated. For example, the force-sensing circuit maybe used to determine an amount or magnitude of force being applied ateach measured location, such as using the weighted centroid techniquedescribed with respect to the FIG. 8. In some embodiments, theoperations of method 1100 are repeated multiple times. In someembodiments, the operations of method 1100 are repeated so long as theforce sensitive device is powered on.

FIG. 11B depicts another process for operating a device having a forcesensor. The process may be applied using the force sensors describedabove with respect to FIGS. 2A, 2B, 3-8, discussed above.

FIG. 11B depicts another exemplary flow chart for a process 1150 thatincludes flow points and operational steps or functions. Although theseflow points and operations are shown in a particular order, in thecontext of a more generalized technique, there is no particularrequirement that the order of the operations must be followed as shown.Similarly, although these flow points and operations are shown performedby a general purpose processor in a device, in the context of a moregeneralized approach, there is no particular requirement for any suchlimitation. In some cases, prior to performing the operations of process1150, the electronic device has been turned on and the operating systemhas been loaded and is running. Also, the relevant hardware including,for example, touch screen sensors, display devices, and force sensordevices may have been powered and may have been initialized.

At operation 1155, a charge signal is transmitted to a force-sensitivestructure. In a typical implementation, the charge signal includes aseries of charge pulses is transmitted to one of the capacitive platesin a force-sensitive structure. Each charge pulse comprises a momentarychange in the voltage applied to the capacitive plates of theforce-sensitive structure resulting in an induced current across theplates. In some instances, the charge signal is an alternating current(AC) that is applied across the capacitive plates of the force-sensingstructure. In many cases, if the charge signal is a discrete chargepulse, the charge pulse is transmitted at regular intervals during theoperation of the device. If the charge signal is an alternating current,the charge signal may be transmitted continuously during operation. Ineither case, operation 1155 is typically performed simultaneously withoperations 1160, 1165, and 1170, described below.

At operation 1160, a first capacitance is measured for theforce-sensitive structure. Typically, the capacitance is measured whilethe force-sensitive structure is in an uncompressed or unactuated state.For example, the measurement of operation 1160 may be taken when thedevice is stationary and is not being touched by an operator. In somecases, multiple measurements are taken over a period of time and acomposite or average capacitance value is determined.

At operation 1165, a force is applied to the device. In accordance withthe embodiments described above with respect to FIGS. 2A, 2B, 3-8, auser may touch the cover glass of a device applying a force at alocation on the cover glass. The user may touch the device with afinger, stylus, pen, or the like. In some cases, multiple touches areapplied to the cover glass at the same time in accordance with amulti-touch gesture or user input. In accordance with the embodimentsdescribed above with respect to FIGS. 2A, 2B, 3-8, an applied forcetypically results in the compression or deflection of a force-sensitivestructure resulting in a relative change in position of the twocapacitive plates.

At operation 1170, a second capacitance is measured for theforce-sensitive structure. Typically, the capacitance is measured whilethe force-sensitive structure is in a compressed or deflected state dueto the force applied in operation 1165, described above. In some cases,multiple measurements are taken over a period of time and a composite orrepresentative capacitance value is determined.

At operation 1175, a force is estimated using the first and secondcapacitance measurements. In accordance with the embodiments describedabove with respect to FIGS. 2A, 2B, 3-8, an applied force results in achange in the position of the two capacitive plates, thus changing thecapacitance of the force-sensitive structure. In operation 1175, thechange in capacitance is correlated with or used to compute an estimatedforce. For example, if compressible element of a force-sensitivestructure behaves as a linear force spring, the change in capacitance(which is proportional to the change in distance between the capacitiveplates) will be proportional to the change in force. Because thematerial properties, such as the spring rate, of the compressibleelement are known the amount of force can be estimated as the differencebetween the first and second capacitance measurements multiplied by aconstant. In some embodiments, the operations of method 1150 arerepeated multiple times. In some embodiments, the operations of method1150 are repeated so long as the force sensitive device is powered on.

-   -   6. Electrical Connection to a Force Sensor and Method of        Manufacturing

In accordance with certain embodiments described above, a capacitiveforce sensor typically includes a force-sensitive stack having twocapacitive plates separated by an intermediate, compressible element. Ina typical implementation, a charge signal is applied to at least one ofthe capacitive plates and a capacitive measurement is taken. To deliverboth the charge signal (drive signal) and receive the capacitivemeasurement (sense signal) from the capacitive plates, theforce-sensitive structure is typically connected to other elements ofthe system by an electrical connection. To facilitate assembly duringmanufacturing, it may be advantageous that the electrical connection bea detachable electrical connection formed from a flexible conduit.

FIG. 12 depicts an example touch device 1200 having two force-sensingstructures 1210, 1220 located around the perimeter of a display element1202 or a portion thereof. The two force-sensing structures 1210, 1220are electrically connected to an electrical connector tail 1250. In thisexample, each of the two force-sensing structures (1210, 1220) is formedfrom a first and second capacitive plate separated by an intermediate,compressible element. Generally, the force-sensing structures 1210 and1220 can be used to determine a magnitude of a touch on a surface of thedevice. As explained above with respect to FIGS. 3-5, a force applied tothe device compresses or deforms the compressible element, changing thedistance between the first and second capacitive plates. The change indistance can be measured as a change in capacitance between the twoplates using force-sensing circuitry. Accordingly, the two structures1210, 1220 cooperate to sense a force; in this manner, they may bereferred to as either separately or together as a “force-sensingstructure.”

The electrical connector tail 1250 can be used to electrically couplethe two force-sensing structures 1210, 1220 with the force-sensingcircuitry, which may be located on a separate circuit component withinthe device. In some cases, it may be advantageous that the electricalconnector tail 1250 is formed from a flexible conduit to facilitateconnection with the force-sensing circuitry. For example, the electricalconnector tail 1250 may be formed from a laminate of polyimide materialsthat have been printed or formed with electrical conductive traces. Insome cases, it may be further advantageous that the flexible conduit beconfigured to bend easily to facilitate routing within the limited spaceof the device enclosure. To improve the flexibility or bend radius ofthe connector tail 1250, it may be advantageous to eliminate or removethe intermediate, compressible element in at least an end portion of theconnector tail 1250. Removing the intermediate, compressible element mayalso facilitate electrical connection with one or more internal surfacesof the electrical connector tail 1250.

FIG. 13 depicts a cross-sectional view along line 3-3 of the electricalconnector tail 1250. As shown in FIG. 13, the electrical connector tail1250 is formed from four circuit layers 1211, 1212, 1221, 1222. In thisexample, each of the circuit layers includes at least one flexibledielectric layer and at least one flexible conductive layer. Theflexible dielectric layer may be formed from a polyimide sheet and theelectrical conductive layer may be formed from a metal film ormetallized trace material. Further, in this example, each of the circuitlayers is electrically connected with a capacitive plate of one of theforce-sensitive structures 1210, 1220 (depicted in FIG. 12). Forexample, the electrical conductive layer of circuit layer 1211 may beelectrically connected to a first (upper) capacitive plate of theforce-sensitive structure 1210. Similarly, the electrical conductivelayer of circuit layer 1212 may be electrically connected to a second(lower) capacitive plate of the force-sensitive structure 1210.Similarly, the circuit layers 1221 and 1222 are electrically connectedto a first (upper) and a second (lower) capacitive plate, respectively,of the force sensitive structure 1220. In this example, each of thecircuit layers 1211, 1221, 1222, and 1212 are electrically coupled to arespective terminal 1213, 1223, 1224, and 1214.

Alternatively, one or more of the circuit layers 1211, 1221, 1222, and1212 may serve as a ground layer for the force-sensitive structure 1210.In one example either of both of the outer circuit layers 1211 or 1212are held at a constant voltage during the operation of the sensor to actas an electromagnetic shield. In some cases, the outer circuit layers1211 or 1212 are connected to ground during the operation of the sensorto facilitate electromagnetic shielding. One or more of the outercircuit layers may serve as a ground shield, depending on the locationof the source of the interference. In some cases, one or more additionalground shield circuit layers are added to the force-sensitive structure.These additional ground shield layers may be added, for example, to theouter surfaces of the outer circuit layers 1211 and 1212. In oneexample, the conductive traces in any ground shield layer may extentsubstantially across the entire surface of the circuit layer to maximizethe area that is shielded by the ground shield layer.

As shown in FIG. 13, the two circuit layers 1211 and 1221 are separatedfrom the other two circuit layers 1212, and 1222 by the intermediatecompressible layer 1230. In this example, the compressible layer 1230serves as the compressible element in the force sensors 1210, 1220. Asalso shown in FIG. 13, the compressible layer 1230 does not extend intoan end portion 1255 of the electrical connector tail 1250. As shown inFIG. 13, a void region 1350 is formed between the pairs of circuitlayers. In some embodiments, the tail may lack any intermediatecompressible layer.

As explained above, this configuration may be advantageous from a fewaspects. First, because there is no material connection between theupper and lower pairs of circuit layers, the bendability of theelectrical connector tail 1250 is improved, which may facilitate asmaller bending radius. Additionally, because there is no materialbetween the pairs of circuit layers, additional internal electricalterminals 1223 and 1224 may be used for electrical connections. Thisreduces the need for circuit vias or additional electrical routing thatmay otherwise be required to electrically connect the electricalconductive layers of internal circuit layers 1221, 1222 to an externalterminal.

The tail 1250 may extend from the force-sensing structures 1210, 1220and bend one or more times to connect to a flex or other electricalconnection within the device. As one non-limiting example, the tail 1250or, more appropriately, the flexible dielectric and flexible conductivelayers may bend in a serpentine fashion to each an interconnect. Twoseparate structures may form the tail; each such structure may be formedfrom one flexible dielectric and one flexible conductive layer.Generally, the two tail structures may follow different paths insofar asone extends from the upper force-sensing structure 1210 and one from thelower force-sensing structure 1220. Nonetheless, the constituentstructures of the tail 1250 are typically routed such that they do notexperience any force exerted on a cover glass, housing or other externalforce-sensitive surface. Thus, the tail 1250 may not present a secondarypath for an exerted force to bypass the force sensor which, in turn, mayincrease the accuracy of the force sensor. Likewise, other components ofthe electronic device may be structured such that they do not absorb ordivert force exerted against a force-sensitive surface of the electronicdevice.

While the device 1200 depicted in FIG. 12 includes two force-sensingstructures located around the periphery of a display element 1202, analternative embodiment may include only a single force-sensingstructure. In this case, the electrical connector tail may only includetwo conductive layers (on two circuit layers). In other alternativeembodiments, a device may include more than two force-sensing structuresand the electrical connector tail may have multiple conductive layers tofacilitate connection with each of the force-sensing structures.

FIG. 14 depicts an example process 1400 for manufacturing a force sensorhaving an electrical connector tail. The process 1400 can be used tomanufacture the force sensors 1210, 1220 having an electrical connectortail 1250 in accordance with the embodiments of FIGS. 12 and 13. Theprocess 1400 may also be used to manufacture force sensors having avariety of configurations, including configurations having a single pairof conductive layers.

In operation 1405, a first circuit layer is obtained. In this example,the first circuit layer comprises at least a first flexible conductivelayer and a first flexible dielectric layer. With reference to FIG. 13,the first circuit layer may include one of either of the circuit layerspairs 1211, 1221 or 1222, 1212. In some cases, the first circuit layermay be obtained by forming the first conductive layer on the firstdielectric layer. The conductive layer may be formed by, for example,bonding a metal foil to a surface of the first dielectric layer. In somecases, the conductive layer may be formed by a deposition or sputteringprocess that deposits a conductive material onto the dielectric layer.In one example, the conductive layer also forms one or more of thecapacitive plates used for the force sensor. In some cases, the firstcircuit layer is pre-manufactured and obtained as a sheet or die-cutcomponent.

In operation 1410, a second circuit layer is obtained. In this example,the second circuit layer also comprises at least a second flexibleconductive layer and a second flexible dielectric layer. With referenceto FIG. 13, the second circuit layer may also include one of eithercircuit layer pairs 1211, 1221 or 1222, 1212 (that is also separatedfrom the first circuit layer by the intermediate compressible layer1230). As described above, the first circuit layer may be obtained byforming the first conductive layer on the first dielectric layer bylaminating a metal foil or depositing a conductive material onto asurface of the dielectric layer. The second circuit layer may also bepre-manufactured as a sheet or die-cut component.

In operation 1415, a laminate structure is formed. In particular, alaminate structure is formed such that the compressible layer isdisposed between the first and second circuit layers. With reference toFIG. 13, an exemplary laminate structure includes the four circuitlayers 1211, 1221, 1222, 1212 and the compressible layer 1230. In manycases, other layers are formed as part of the laminate structure. Forexample, additional circuit layers, adhesive layers, and coatings may beformed as part of the laminate structure. In particular, an adhesivelayer is typically used to bond the intermediate compressible layer withthe other, adjacent components of the laminate structure. It is notnecessary that either the first or second circuit layers (obtained inoperations 1405 and 1410) be immediately adjacent or bonded directly tothe compressible layer.

Operation 1415 may be performed by, for example, placing pressuresensitive adhesive (PSA) layers between the components of the laminatestructure. The laminate may then be subjected to a pressing operation tobond the layers. In some cases, heat or other curing techniques may beemployed to bond the layers together. In some embodiments, the PSA maybe applied, all layers bonded, and then the structure die cut to itsfinal form.

Operation 1415 may also be performed using an injection or insertionmolding process. In this case, the first and second circuit layers maybe laminated or pre-formed with other layers or components. The layersmay then be placed in opposite halves of an injection mold cavity andthe intermediate compressible layer may be formed between the layers byinjecting a molten or liquid material into the injection mold. In oneexample, a spacer element is placed between the first in second circuitlayers to hold the first and second circuit layers against therespective halves of the injection mold. The spacer element may beapproximately the same thickness as the final dimension of thecompressible layer. In one example, the spacer element is compressibleand is slightly larger than the final dimension of the compressiblelayer to be injection molded between the first and second circuitlayers. In this case, the spacer element exerts a force against thefirst and second circuit layers, which are pressed against respectivecavity walls of the injection mold. By pressing the circuit layersagainst the cavity walls, the injected molded material is more likely tofill the area between the circuit layers rather than filling an areabetween the circuit layers and the cavity walls. In one example,multiple spacer elements are used, each spacer element formed from asemi-circular ring. The spacer elements may be placed near the injectionpoint of the mold, which is typically near the center of the part. Thespacer elements can then be removed by die-cutting the center portion ofthe part, which may also facilitate the creation of a viewing area forthe display.

As part of operation 1415, one or more electrical vias may be formedbetween the various layers of the laminate structure. In some cases,electrical vias are formed through the compressible layer to connectcircuit layers that are disposed on opposite sides of the compressiblelayer. The vias may be formed by, for example, the addition ofconductive pillar elements that electrically connect the conductivelayers of different circuit layers. Additionally or alternatively,conductive regions within the compressible layer may be formed and thenreflowed or otherwise electrically connected with conductive layers ofthe laminate structure.

In some cases, the laminate structure that is formed in operation 1415is cut to form the force sensor having an electrical connector tail. Forexample, if the first and second circuit layers (obtained in operations1405 and 1410) are formed as a solid sheet of material, the laminatestructure may be die cut to form the desired geometric profile featuresof the force sensor. Specifically, a center portion may be cut out ofthe middle of the laminate structure to facilitate installation with adisplay element. Thus, the display element will be visible through thehole created in the middle of the laminate structure. As mentionedabove, if the laminate structure includes spacer elements used for aninjection molding process, they may be removed by this die cuttingoperation. Additional cuts may be performed to form the connector tailportion of the force sensor.

The cutting operation may be optional if, for example, the first andsecond circuit layers (obtained in operations 1405 and 1410) have beenpre-cut or have been formed in the desired geometric profile shape. Inthis case, operation 1415 may also include an indexing operation toalign the layers of the laminate structure.

In operation 1420, a portion of the compressible layer is removed fromthe laminate structure. In this example, a portion of the compressiblelayer located in an end portion of electrical connector tail is removedfrom the laminate structure leaving a void region between the first andsecond circuit elements. As explained above with respect to FIGS. 12 and13, removal of the compressible layer may improve the flexibility orbendability of the laminate structure. It may also provide access toterminals or electrical connections on circuit layers that are internalto the laminate structure.

Removing the compressible layer may be accomplished using one or moretechniques. In a first example, the compressible layer is perforated orpre-cut near the end portion of the electrical connector tail. Also,within the end portion of the electrical connector tail, the pressuresensitive adhesive or other bonding layer may be omitted between thecompressible layer and the adjacent layers of the laminate structure. Inthis case, the pre-cut or perforation and the absence of a bonding layerallows the portion of the compressible layer in the end portion of theelectrical connector tail to be removed.

In a second example, one or more layers of the laminate structure aredelaminated or stripped from the compressible layer exposing thecompressible layer. In this case, as secondary cut operation may beperformed to remove the portion of the compressible layer in the endportion of the electrical connector tail.

In a third example, the compressible layer may be cut from the endportion of the electrical connector tail without first delaminating orstripping layers of the laminate structure. For example, the portion ofthe compressible layer within the end portion of the connector tail maybe removed by passing a knife or cutting implement between the layers ofthe laminate structure.

As an alternative to operation 1420, the laminate structure may beformed such that the end portion of the electrical connector tail doesnot include the compressible layer. For example, if the laminatestructure is formed using an injection or insertion molding process, aninsert mold element may be placed in the end portion of the electricalconnector tail preventing the formation of a compressible layer in thisregion. In this case, the laminate structure is formed with a voidregion between the first and second circuit layers.

As described above, the process 1400 may also be used to manufactureforce sensors having a variety of configurations, includingconfigurations having a single pair of conductive layers. For example, aforce sensor having only two circuit layers (one on each side of theintermediate compressible layer) may be formed using process 1400.Alternatively, a force sensor having multiple circuit layers formed oneither side of the intermediate compressible layer may also be formedusing process 1400.

The operations of process 1400 are provided as one example. However, aforce sensor may also be formed by omitting one or more of theoperations described above. For example, depending on how the laminatestructure is created, it may not be necessary to perform operation 1420to remove a portion of the compressible layer.

In certain embodiments, the tail may be connected to a flex, circuitboard or other electronic contact. In some embodiments, the entireforce-sensing structure may be placed into an oven to bond the tail tothe electrical contact through, for example, a surface-mount technology(SMT) process. In some embodiments, the SMT process may heat the tail(or portions thereof) and/or the electrical contact to 200 degrees ormore. This elevated temperature may have deleterious effects on thesilicone of the force-sensing structure, however. Thus, theforce-sensing structure may be placed in a heat-resistant envelope,pouch or other container with the tail extending outwardly therefrom.Thus, when the oven is heated for the SMT process, the tail may beheated to the appropriate temperature while the silicone and otherlayers of the force-sensing structure may be maintained at a temperaturethat does not cause damage. Further, it should be appreciated that theforce-sensing structure may not be singulated or cut into its final formprior to heating in the oven.

FIG. 15A depicts another embodiment 1500 of a force-sensing electronicdevice. Similar to other embodiments described herein, the embodiment1500 may include and electronic device having a cover 1505 positionedover a display stack 1515, which may be configured to detect the touchof a force on the surface of the cover 1505. The cover 1505 may beformed from a variety of materials including, for example, glass,polycarbonate or other plastic, sapphire and the like. The display stack1515 may include a liquid crystal display (LCD), organic light omittingdiode (OLED), or other electronic display component.

In some embodiments, the cover 1505 may move with respect to the housing1510. When a force is exerted on the cover 1505, by, for example, thetouch of a user, the cover 1505 may travel downwardly. It should beappreciated that the entirety of the cover 1505 may travel in such afashion, rather than only deflecting locally while edges of the cover1505 remain substantially immobile. Whether the cover 1505 deflectslocally or not may depend on the relative stiffness of the cover 1505and the components/elements positioned below the cover 1505.

In some embodiments, the downward travel of the cover 1505 likewisemoves the display stack 1515 downward, which in turn may impact and/orcompress a sheet sensor 1520 positioned beneath the display stack 1515.The sheet sensor 1520 may include a capacitive-plate type force sensor,strain gauge sensor, or other force-sensitive sensor, and may generallybe referred to as a force sensing structure, sensor, or sheet sensor. Ingeneral, the sheet sensor 1520 may extend over a substantial portion ofthe display stack 1515. In some cases, the sheet sensor 1520 is formedfrom an array or series of force-sensing elements that are disposedthroughout the area of the sheet sensor 1520.

As shown in FIG. 15A, the sheet sensor 1520 may substantially abut thedisplay stack 1515. In some embodiments, the sheet sensor 1520 may beseparated therefrom by an air gap and/or other components or layers incertain embodiments. In some embodiments, the sheet sensor 1520 may beaffixed directly to an element of the display stack 1515.

The sheet sensor 1520 may be supported by a plate 1525 positioned belowthe sensor 1520 opposite the side facing the display stack 1515. In someembodiments the plate 1525 may be rigid or substantially rigid, while inother embodiments the plate 1525 may be flexible. Typically, althoughnot necessarily, the sheet sensor 1520 is affixed to the plate 1525. Insome embodiments, the plate 1525 may be fixed relative to the housing1510 of the device. In some embodiments, the plate 1525 may be amid-plate providing structural support and/or stiffness to the housing1510 of the electronic device 1500, while in other embodiments the plate1525 may be used primarily or solely to support the sheet sensor 1520.In still other embodiments, other electronic components (not shown) mayshare the plate 1525 with the sheet sensor 1520.

As the cover 1505 and display stack 1515 move downward, the sheet sensor1520 may be compressed. This compression may be sensed by the sheetsenor 1520 and a corresponding output generated. For example, the sheetsensor 1502 may have first and second capacitive plates or arrays 1530,1535 (as used herein, the term “plate” is intended to cover an array aswell) defining an upper surface and a lower surface of the sheet sensor,or otherwise positioned in an upper and lower region of the sensor. Thefirst and second capacitive plates 1530, 1535 may be separated from oneanother by a compressible inner layer 1540, such as silicone or acompliant gel or polymer.

In some embodiments, the first and second capacitive plates 1530, 1535are operatively coupled to a sensing circuit that is configured toestimate the force of a touch on the cover based on a change incapacitance between the first and second capacitive plates 1530, 1535.In some implementations, sensing circuit is configured to generate adrive signal or electrical current that is used to detect and measurechanges in capacitance between the first and second capacitive plates1530, 1535. As the first capacitive plate 1530 moves toward the secondcapacitive plate 1535, the reduction in distance may correspond to achange in capacitance between the plates, which may be correlated to theforce exerted on the cover 1505.

It should be appreciated that the sheet sensor 1520 may operate as aself-capacitance or mutual capacitance sensor to measure force in thisfashion. Accordingly, in a mutual capacitance configuration, one of thefirst and second capacitive plates may be a drive plate and the othermay be a sense plate. In a self-capacitance configuration, one of thefirst and second plates maybe a ground or shield layer while the otheris a sense plate. Further, one or both plates of the sheet sensor 1520may be formed in a pixel pattern (as may the sheet sensor 1520 itself)in order to locally register the application of a force and provide alocalized region at which a force is applied.

In an embodiment having a flexible or deflectable plate 1525 supportingthe sheet sensor 1520, changes in capacitance may still be measured solong as the layers of the sheet sensor 1520 compress, even if the plate1525 itself flexes. Similarly, in embodiment having an air gap betweenthe sheet sensor 1520 and display stack 1515, a force of a touch may notbe sensed until the display stack moves far enough to compress or impactthe sheet sensor.

It should be appreciated that the sheet sensor 1520, as shown in FIG.15A, need not be transparent insofar as it is located beneath thedisplay stack 1515. Further, such a configuration may be suitable notonly for use with a display stack having an LED or LCD display, but alsowith a display stack incorporating an OLED display layer.

FIG. 15B depicts an alternative embodiment 1500B of the embodiment shownin FIG. 15A. In this embodiment 1500B, foam 1545 or other compliantmaterial or compliant layer may be placed between the display stack 1515and sheet sensor 1520. The foam 1545 may generally stiffen the displaystack 1515 and/or cover 1505 and thus prevent the entire stack/glassfrom moving downward. Instead, when a force is exerted on the cover1505, the foam 1545 may deform locally and thereby concentrate thedeformation and/or force in a localized region, which may in turnenhance the force-sensing capabilities of the embodiment 1500B. Itshould be appreciated that any suitable material may be placed betweenthe display stack 1515 and the sheet sensor 1520; foam is but oneexample material.

In some embodiments, a compliant environmental seal 1501 may bepositioned between the cover 1505 and housing 1510. The compliant gasketmay prevent the ingress of dirt, dust and the like into the interior ofthe electronic device 1500B, but may still permit downward travel of thecover 1505 and display stack 1515. In alternative embodiments, thegasket 1550 may be relatively rigid and may cooperate with the foam 1545(or operate in the absence of the foam 1545) to restrict downward motionof the cover 1505 at one or more edges, with the net result that thecover may deflect locally instead of traveling as a whole. Force maystill be sensed in such an embodiment through localized compression ofthe sheet sensor 1520.

In some embodiments, a portion or all of the region occupied by thegasket 1550 may be coated with an oleophobic material. The oleophobicmaterial may serve as a barrier against, or repel, oils, dust, dirt andother similar materials from entering the housing 1510 and/or impactingthe force-sensing structure 1520. In this fashion the coating may serveto maintain operation of the force-sensing structure over time. Coatingsother than an oleophobic coating may be used; other dust- and/or oil-and/or dirt-repellent coatings may be used in different embodiments.

FIG. 15C depicts still another embodiment of a force-sensitiveelectronic device 1500. This embodiment is generally similar to that ofFIG. 15B, except for the structure of the sheet sensor 1520C. Here, thesheet sensor 1520C may be patterned from one or more strain gaugesrather than taking the form of a capacitive sensor. Individual straingauges may be arranged in an array, grid, or other pattern to form thesheet sensor 1520C. The strain gauges may be formed from a material thatchanges electrical properties or produces an electrical response due toa deflection of the sheet sensor 1520C. The strain gauges may be formed,for example, from a resistive material, piezoelectric resistivematerial, piezoelectric material, and the like. The strain gauges mayalso be formed as an array of strain gauge elements, each elementcomprised of a series of traces or patterns that may be configured todetect a localized strain or deflection.

As force is exerted on the cover 1505, it is transferred through thedisplay stack 1515, through the foam 1545 (or other compliant layer),and to the strain gauge(s) of the sheet sensor 1520C. The strain gaugesmay experience an increase in strain due to the exerted force; thisincrease in strain may be correlated to determine the magnitude of theexerted force as generally described elsewhere herein. In someembodiments, the sheet sensor 1520C is operatively coupled to sensecircuitry that is configured to monitor and detect changes in anelectrical property or measure and electrical response of the straingauges of the sheet sensor 1520C. For example, the sense circuitry maybe configured to detect a change in resistance and/or charge due to adeflection of the sensor sheet 1520C.

In the embodiments shown in FIGS. 15A-15C, the cover and display stackare generally free to translate with respect to the housing. In someembodiments, the cover and/or display stack may be adhered to thehousing or otherwise fixed with respect to the housing, such that forceexerted on the cover causes local deformation of the cover rather thantranslation. In such embodiments, force may be relatively localizedinsofar as the boundary conditions of the cover prevent motion. Sincethe cover may still deflect locally, a force may still be transmittedthrough the various layers and sensed by the force sensor (e.g., thesheet sensor).

FIG. 15D depicts a close-up of area 15D in FIG. 15C, showing oneembodiment of a compliant layer 1545D positioned between the sheetsensor 1520 and the base of the display stack 1515. In thecross-sectional view of the electronic device 1500 shown in FIG. 1, thecompliant layer 1545D is formed from a series or array of pillar-likestructures 1560 sandwiched between an upper compliant substrate 1555 anda lower rigid substrate 1565 made of glass or the like. (In someembodiments, the lower substrate may also be compliant). In certainembodiments, the upper sheet 1555 may be formed from silicone, as maythe pillar structures 1555. A sheet sensor 1520C is located beneath thelower substrate 1565. In the present embodiment, the sheet sensor 1520Cis formed of one or more strain gauges, as discussed above with respectto FIG. 15C. The sheet sensor 1520C may be supported by a sense plate1525, as generally discussed above.

In some implementations, the pillar structures 1555 may deform underdownward pressure exerted on the compliant layer 1545C by the displaystack 1515, or any other element of the electronic device 1500C thatexerts pressure on the compliant layer 1545D. One or more void spaces1550 may be defined between and/or around the pillars 1560. For example,adjacent pillars 1560 may be separated by a void space 1550 and eachvoid space 1550 may be separate and distinct. As another option, asingle void space 1550 may encompass all the pillars 1560. Differentconfigurations of void spaces and pillar structures are thuscontemplated.

As the pillar structures 1555 deform, the top sheet 1555 moves closer tothe bottom sheet 1565 and the resistance of the pillar structure tofurther collapse increases. Further, the strain exerted on the sheetsensor 1520C through the compliant layer 1545D generally increases,causing the strain gauge output to increase. This increase in output maybe correlated to a force exerted on the exterior of the housing.

In some embodiments, the void space or spaces 1550 may be filled with anoptically transparent or near-transparent fluid, gel or the like(collectively, “fluid”). In some embodiments, the fluid may be opticallyindexed matched to the optical index of the pillar structures. That is,in certain embodiments, the index of refraction of the fluid may matchor approximate that of the pillar structures 1555. In such anembodiment, the combination of fluid in the void spaces 1550 and pillarstructures 1560 may render the compliant layer 1545D opticallytransparent and/or near-invisible. This may be useful when the displayis an OLED display, for example.

In yet another embodiment and as shown in FIG. 15E, the compliant layer1545D may separate a lower capacitive sensing array 1570 from an uppercapacitive sensing array 1575. In such an embodiment 1500E, thecapacitive sensing arrays 1570, 1575 may operate as described elsewhereherein, such that one array is a drive array (or reference array) andone is a sense array. The compliant layer 1545D may serve to prevent thetwo layers from approaching too close to one another and thus prevent,or at least reduce the likelihood of, contact between the two layersand/or excessive capacitive coupling between the two layers, which mayresult in inaccurate force measurement.

FIG. 16 depicts a partial cross-section of another embodiment of aforce-sensing electronic device 1630. This embodiment may include aforce-sensing structure 1600 similar to that shown in FIGS. 2A and 3,and described elsewhere herein. For example, the force-sensing structure1500 may be configured with multiple capacitive layers separated by adeformable middle body, as generally discussed with respect to FIG. 3and/or the variants shown in FIGS. 4-6. The force-sensing structure 1600may take the form of a gasket any may be located between the cover 1505and a housing 1510. In one embodiment, the portion of the housing 1510adjacent the cover 1505 may include a bezel or bezel portion.

The force-sensing structure 1600 may extend partly or fully about aperimeter of the electronic device, cover, and/or portion of either.Alternately, multiple force-sensing structures 1600 may cooperate toextend partly or fully about a perimeter of the electronic device 1630,cover, and/or portion of either. In some embodiments, the force-sensingstructure 1600 may be configured to prevent the ingress of contaminantsinto the interior of the housing 1510 and, therefore, may also functionas a gasket. In some cases, the combination gasket and sensor isreferred to as a strain-sensitive gasket or gasket force-sensingstructure.

As with prior embodiments, the force-sensing structure 1600 maycapacitively sense a distance between the first and second plates 1620,1625 or other sensor structures; the output of the force-sensingstructure 1600 may be correlated to a force by a sensing circuit,processor, or other electronic component of the force-sensing electronicdevice 1630. In some embodiments, the force-sensing structure 1600 isoperatively coupled to sense circuitry that is configured to detect andmeasure changes to an electrical property of the force-sensing structure1600, which may be correlated to the force of a touch on the cover 1505.

In addition to the force-sensing structure 1600 generally positionedbetween the cover 1505 and bezel or housing 1510, the present embodimentmay incorporate a force-sensitive sheet sensor 1520. The sheet sensor1520 is generally similar in configuration and operation to any of thesheet sensors described above with respect to FIGS. 15A-15D.

As shown in FIG. 16, the sheet sensor 1520 may be separated from thedisplay stack by a small air gap. Additionally or alternatively, thesheet sensor 1520 may be separated from the display stack by acompressible layer similar to the compressible layer described abovewith respect to FIGS. 15B-E. When the cover 1505 and display stack 1515deflect in response to a force, the gasket force-sensing structure 1600may compress and sense force, as generally described herein. To preventbottoming out of the cover and display stack when a force is appliedaway from the edges of the cover, the sheet sensor 1520 may be included.When the display stack and cover deform sufficiently, they may contactthe sheet sensor 1520 and transmit force thereto. The two force sensors1600 and 1520 may cooperate to determine a force. For example, theoutput of both force sensors may be taken and manipulated to determinethe force exerted on the cover. In this manner, the dynamic forcesensing range of the device 1500 may be extended to sense and react toforces that would otherwise be sufficiently large to cause the cover tobottom out and the single gasket sensor 1600 to register a maximumvalue. In some embodiments, the air gap is configured to at leastpartially collapse in response to a force of a touch that exceeds afirst threshold. In some implementations, the first threshold is lessthan a second threshold that corresponds to a maximum force that can bepractically or reliably detected by gasket force-sensing structure 1600.

FIG. 17 depicts yet another embodiment of an electronic device 1700 thatmay employ a sheet or pad sensor 1520 for capacitively measuring a forceexerted on a cover 1505 (or, in other embodiments, a portion of ahousing or a different type of input surface). Generally, the structureand operation of the sheet sensor 1520 is similar to that describedherein with respect to prior figures.

In addition to the upper and lower capacitive arrays of the sheet sensor1520, a second capacitive sense layer/array 1705 may be placed withinthe display stack 1515. In one embodiment, the second capacitive senselayer 1705 may be formed from indium-tin-oxide, silver nanowire, PEDOT,or any other suitable conductive material. In certain embodiments, itmay be desirable for the second capacitive sense layer 1705 to betransparent.

In the embodiment 1700 of FIG. 17, the second capacitive sense layer1705 may be placed relative to the display stack 1515. The capacitivesense layer 1705 may, in some instances, function as a capacitive touchsensor for sensing the location of a touch on the cover 1505. In someembodiments, the capacitive sense layer 1705 is positioned above abacklight unit 1710. If the second capacitive sense layer 1705 istransparent or nearly so, it may not interfere with the operation of thebacklight unit 1710 and/or the remainder of the display stack 1515.

As shown in FIG. 17, an air gap may be located between the capacitivesense layer 1705 and the sheet sensor 1520. Additionally oralternatively, the sheet sensor 1520 may be separated from thecapacitive sense layer 1705 by a compressible layer similar to thecompressible layer described above with respect to FIGS. 15B-E.

As a force is exerted on the cover 1505 (or housing or input surface, insome embodiments), the cover and display stack 1515 are moved closer tothe sheet sensor 1520. Thus, the second capacitive sense layer 1705 islikewise moved closer to the sheet sensor 1520. Accordingly, acapacitance between at least a portion of the second capacitive senselayer 1705 and the upper capacitive array 1530 of the sheet sensor 1520may increase with such motion. Further, because the cover 1505, displaystack 1515 and second capacitive sense layer 1705 may deform locally inresponse to the force, the capacitance may increase (or increase more)in the general region corresponding to the exerted force. This change incapacitance may be used to estimate the applied force, as generallydescribed elsewhere herein.

Under sufficient force, the backlight unit 1710 (or other base of thedisplay stack) will contact the upper surface of the sheet sensor 1520.Once this occurs, the capacitance between the second capacitive senselayer 1705 and the upper capacitive array 1530 of the sheet sensor 1520will generally reach a maximum value. Additional force may cause thesheet sensor 1520 to compress, thereby moving at least a portion of theupper capacitive array 1530 closer to the lower capacitive array 1535and increasing a capacitance between these two elements, at least withina given region. Thus, even though the capacitance between the secondcapacitive sense layer 1705 and the upper capacitive array 1530 may beat maximum or near-maximum value, the increase in capacitance betweenthe arrays 1530, 1535 of the sheet sensor 1520 may be used to determineestimates of an exerted force.

In some embodiments, sensing circuitry is operatively coupled to thecapacitive sense layer 1705 and the sheet sensor 1520. The sensingcircuitry may be configured to estimate the force of a touch on thecover based on a change in mutual capacitance between the capacitivesense layer 1705 and the upper and/or capacitive plate of the sheetsensor 1520. In some embodiments, the sensing circuitry may beconfigured obtain a first capacitance between the upper capacitive plateand the lower capacitive plate of the sheet sensor and also obtain asecond capacitance between the upper capacitive plate and the capacitivesense layer. An estimate of a force of a touch on the cover may becomputed or generated using the first and second capacitances measuredusing the sensing circuitry.

It may be considered, then, that the capacitance between the secondcapacitive sense layer 1705 and the upper capacitive array 1530 may beused to determine or estimate an exerted force between zero and somefirst threshold value, and the capacitance between the upper and lowercapacitive arrays 1530, 1535 of the sheet sensor 1520 may be used todetermine an exerted force between the first threshold value and asecond threshold value. This combination of sensing structures mayprovide force sensing about a wider range of values than may be achievedby the use of a single sensor.

It should be appreciated that embodiments described herein may measurechanges in force, thereby providing a non-binary or even substantiallycontinuous input to an associated electronic device, corresponding tochanges in distance or less than 2 microns between two capacitivestructures or arrays. Thus, although one or both of the capacitivestructures or arrays may move with respect to the other, the motion maybe imperceptible to a human interacting with the device. Changes indistance on the measure of nanometers may correspond to approximatelyone gram of force being exerted on a surface, as one non-limitingexample.

While the present disclosure has been described with reference tovarious embodiments, it will be understood that these embodiments areillustrative and that the scope of the disclosure is not limited tothem. Many variations, modifications, additions, and improvements arepossible. More generally, embodiments in accordance with the presentdisclosure have been described in the context of particular embodiments.Functionality may be separated or combined in procedures differently invarious embodiments of the disclosure or described with differentterminology. These and other variations, modifications, additions, andimprovements may fall within the scope of the disclosure as defined inthe claims that follow.

We claim:
 1. An electronic device, comprising: a cover; a displaydisposed within the electronic device and visible through the cover; aforce-sensing structure disposed within the electronic device on oneside of the cover, comprising: a first capacitive electrode; a secondcapacitive electrode; and a compressible element disposed between thefirst and second capacitive electrodes; and a sheet sensor positioned ona side of the display opposite the cover and configured to be engaged bythe display when a sufficient force is applied at a region of the coveraway from an edge of the cover, wherein: the force-sensing structure andsheet sensor have different force sensing ranges; at least before thedisplay engages the sheet sensor, the force-sensing structure isconfigured to produce a first output that corresponds to an amount offorce applied to the cover; and after the display engages the sheetsensor, the sheet sensor is configured to produce a second output thatcorresponds to the amount of force applied to the cover.
 2. Theelectronic device of claim 1, further comprising: a housing defining anopening, wherein: the cover is disposed over the opening; and theforce-sensing structure forms a gasket between the housing and thecover.
 3. The electronic device of claim 2, wherein: the housing definesa bezel having a shelf surrounding the opening; and the force-sensingstructure is positioned between the shelf and the cover.
 4. Theelectronic device of claim 1, wherein: the sheet sensor comprises: anupper capacitive layer; a lower capacitive layer; and a compressiblelayer disposed between the upper and lower capacitive layers; and theelectronic device further comprises a plate affixed to and supportingthe sheet sensor.
 5. The electronic device of claim 4, wherein an airgap is located between the display and the sheet sensor.
 6. Theelectronic device of claim 1, wherein the force-sensing structurecomprises: a first force-sensing segment disposed under a first edge ofthe cover; and a second force-sensing segment disposed under a secondedge of the cover; and the electronic device further comprisesforce-sensing circuitry operatively coupled to the first and secondforce-sensing segments and configured to: detect changes in capacitivecoupling due to deflection of the first and second force-sensingsegments; and produce a signal that corresponds to the amount of forceapplied to the cover.
 7. The electronic device of claim 1, wherein theforce-sensing structure comprises: a first force-sensing segmentdisposed under a first edge of the cover, the first force-sensingsegment comprising the first capacitive electrode, the second capacitiveelectrode, and at least a portion of the compressible element; a secondforce-sensing segment disposed under a second edge of the cover; a thirdforce-sensing segment disposed under a third edge of the cover; and afourth force-sensing segment disposed under a fourth edge of the cover.8. The electronic device of claim 1, wherein the compressible elementcomprises a compliant sheet having a center opening in which the displayis positioned.
 9. The electronic device of claim 1, wherein thecompressible element comprises multiple segments positioned around acenter opening in which the display is positioned.
 10. An electronicdevice, comprising: a cover; a first force-sensing structure disposedunder at least a first edge of the cover and comprising a first pair ofcapacitive elements separated by a compressible layer; a secondforce-sensing structure disposed under at least a second edge of thecover and comprising a second pair of capacitive elements separated bythe compressible layer; and a sheet sensor positioned below the coverbetween the first and second force-sensing structures and configured tobe engaged when a sufficient force is applied at a region of the coveraway from an edge of the cover; wherein: the first and secondforce-sensing structures have a different force sensing range than thesheet sensor; at least before the sheet sensor is engaged, the first andsecond force-sensing structures are configured to produce first outputsthat correspond to an amount of force applied to the cover; and afterthe sheet sensor is engaged, the sheet sensor is configured to produce asecond output that corresponds to the amount of force applied to thecover.
 11. The electronic device of claim 10, further comprising: athird force-sensing structure disposed under at least a third edge ofthe cover and comprising a third pair of capacitive elements separatedby the compressible layer; and a fourth force-sensing structure disposedunder at least a fourth edge of the cover and comprising a fourth pairof capacitive elements separated by the compressible layer.
 12. Theelectronic device of claim 10, further comprising: a housing defining anopening having a shelf, wherein: the cover is positioned within theopening; and the first and second force-sensing structures arepositioned on the shelf under the cover.
 13. The electronic device ofclaim 10, wherein the compressible layer comprises multiple compressibleelement segments.
 14. An electronic device, comprising: a housingdefining an opening; a cover disposed over the opening; a touch sensordisposed within the electronic device on one side of the cover andconfigured to detect a location of a touch on the cover; aforce-sensitive layer disposed within the electronic device on the oneside of the cover; and a force-sensing structure disposed on a side ofthe force-sensitive layer opposite the cover; and a compressible layerlocated between the force-sensitive layer and the force-sensingstructure; wherein: the force-sensing structure is configured to beengaged when a sufficient force is applied at a region of the cover awayfrom an edge of the cover, the sufficient force causing the compressiblelayer to collapse; at least before the compressible layer collapses inresponse to an amount of force of the touch on the cover, theforce-sensitive layer is configured to produce a first output thatcorresponds to the amount of force; and after the compressible layercollapses in response to the amount of force, the force-sensingstructure is configured to produce a second output that corresponds tothe amount of force.
 15. The electronic device of claim 14, furthercomprising a support structure fixed relative to the housing andsupporting the force-sensing structure.
 16. The electronic device ofclaim 14, wherein: the force-sensitive layer comprises a capacitiveelectrode; the force-sensing structure comprises a first capacitivelayer and a second capacitive layer separated by a second compressiblelayer; and the capacitive electrode of the force-sensitive layer isconfigured to capacitively couple to the first capacitive layer of theforce-sensing structure.
 17. The electronic device of claim 16, wherein:the electronic device further comprises sensing circuitry operativelycoupled to the force-sensing layer and the force-sensing structure; andthe sensing circuitry is configured to estimate an applied force on thecover based on a change in mutual capacitance between the capacitiveelectrode of the force-sensitive layer and the first capacitive layer ofthe force-sensing structure.
 18. The electronic device of claim 17,wherein the sensing circuitry is configured to: obtain a firstcapacitance between the first capacitive layer and the second capacitivelayer of the force-sensing structure; obtain a second capacitancebetween the capacitive electrode of the force-sensitive layer and thefirst capacitive layer of the force-sensing structure; and generate anestimate of the amount of force of the touch on the cover using thefirst and second capacitances.
 19. The electronic device of claim 14,further comprising: a display disposed between the cover and theforce-sensing structure, wherein: the compressible layer is locatedbetween the display and the force-sensing structure.
 20. The electronicdevice of claim 19, wherein: the force-sensitive layer has a differentforce sensing range than the force-sensitive structure.